Nutrient Combinations Sensed by L-Cell Receptors Potentiate GLP-1 Secretion.

Obesity is a risk factor for cardiometabolic diseases. Nutrients stimulate GLP-1 release; however, GLP-1 has a short half-life (<2 min), and only <10-15% reaches the systemic circulation. Human L-cells are localized in the distal ileum and colon, while most nutrients are absorbed in the proximal intestine. We hypothesized that combinations of amino acids and fatty acids potentiate GLP-1 release via different L-cell receptors. GLP-1 secretion was studied in the mouse enteroendocrine STC-1 cells. Cells were pre-incubated with buffer for 1 h and treated with nutrients: alpha-linolenic acid (αLA), phenylalanine (Phe), tryptophan (Trp), and their combinations αLA+Phe and αLA+Trp with dipeptidyl peptidase-4 (DPP4) inhibitor. After 1 h GLP-1 in supernatants was measured and cell lysates taken for qPCR. αLA (12.5 µM) significantly stimulated GLP-1 secretion compared with the control. Phe (6.25-25 mM) and Trp (2.5-10 mM) showed a clear dose response for GLP-1 secretion. The combination of αLA (6.25 µM) and either Phe (12.5 mM) or Trp (5 mM) significantly increased GLP-1 secretion compared with αLA, Phe, or Trp individually. The combination of αLA and Trp upregulated GPR120 expression and potentiated GLP-1 secretion. These nutrient combinations could be used in sustained-delivery formulations to the colon to prolong GLP-1 release for diminishing appetite and preventing obesity.

Colonic Delivery of Nutrients for Sustained and Prolonged Release of Gut Peptides: A Novel Strategy for Appetite Management.

Obesity is one of the major global threats to human health and risk factors for cardiometabolic diseases and certain cancers. Glucagon-like peptide-1 (GLP-1) plays a major role in appetite and glucose homeostasis and recently the USFDA approved GLP-1 agonists for the treatment of obesity and type 2 diabetes. GLP-1 is secreted from enteroendocrine L-cells in the distal part of the gastrointestinal (GI) tract in response to nutrient ingestion. Endogenously released GLP-1 has a very short half-life of <2 min and most of the nutrients are absorbed before reaching the distal GI tract and colon, which hinders the use of nutritional compounds for appetite regulation. The review article focuses on nutrients that endogenously stimulate GLP-1 and peptide YY (PYY) secretion via their receptors in order to decrease appetite as preventive action. In addition, various delivery technologies such as pH-sensitive, mucoadhesive, time-dependent, and enzyme-sensitive systems for colonic targeting of nutrients delivery are described. Sustained colonic delivery of nutritional compounds could be one of the most promising approaches to prevent obesity and associated metabolic diseases by, e.g., sustained GLP-1 release.

Colonic Delivery of α-Linolenic Acid by an Advanced Nutrient Delivery System Prolongs Glucagon-Like Peptide-1 Secretion and Inhibits Food Intake in Mice.

SCOPE: Nutrients stimulate the secretion of glucagon-like peptide-1 (GLP-1), an incretin hormone, secreted from enteroendocrine L-cells which decreases food intake. Thus, GLP-1 analogs are approved for the treatment of obesity, yet cost and side effects limit their use. L-cells are mainly localized in the distal ileum and colon, which hinders the utilization of nutrients targeting GLP-1 secretion. This study proposes a controlled delivery system for nutrients, inducing a prolonged endogenous GLP-1 release which results in a decrease food intake. METHODS AND RESULTS: α-Linolenic acid (αLA) was loaded into thermally hydrocarbonized porous silicon (THCPSi) particles. In vitro characterization and in vivo effects of αLA loaded particles on GLP-1 secretion and food intake were studied in mice. A total of 40.4 ± 3.2% of loaded αLA is released from particles into biorelevant buffer over 24 h, and αLA loaded THCPSi significantly increased in vitro GLP-1 secretion. Single-dose orally given αLA loaded mesoporous particles increased plasma active GLP-1 levels at 3 and 4 h and significantly reduced the area under the curve of 24 h food intake in mice. CONCLUSIONS: αLA loaded THCPSi particles could be used to endogenously stimulate sustain gastrointestinal hormone release and reduce food intake.

Dipeptidyl peptidase-4 and GLP-1 interplay in STC-1 and GLUTag cell lines.

Glucagon like peptide-1 (GLP-1) is an incretin hormone, secreted from L-cells of distal ileum and colon in response to nutrient ingestion in human. GLP-1 plays a major role in gut motility, appetite regulation, and insulin secretion. Dipeptidyl peptidase-4 (DPP4), a serine peptidase, cleaves N-terminal dipeptides of GLP-1, rendering it inactive and responsible for its short half-life. DPP4 is widely expressed in numerous tissues in a membrane bound or soluble form. The enteroendocrine cell lines STC-1 and GLUTag are extensively used as models for in vitro studies, however, the basic parallel characterization between these cell lines is still missing. Previously, we demonstrated that these cell lines exhibit different responses to α-linolenic acid (αLA)-induced GLP-1 secretion. Therefore, we examined the basal and stimulated GLP-1 and DPP4 secretion between the two cell lines. GPR120 and GPR40 are known to bind long chain fatty acids. We found that STC-1 cells secreted significantly more basal and αLA-induced GLP-1 than GLUTag cells. In addition, STC-1 secreted DPP4 and expressed higher amounts of DPP4 and GPR120 than GLUTag cells, while GLUTag cells expressed higher GPR40 protein levels than STC-1 cells. Interestingly, the secreted soluble DPP4 did not change the active GLP-1 concentrations in the buffer group, and only 5.5 % of GLP-1 was degraded in the αLA stimulated group. These results suggested that STC-1 cells have a higher potential to secrete GLP-1 and DPP4 than GLUTag cells, and the membrane bound DPP4 may play a more significant role in the inactivation of GLP-1 secretion.

Inorganic mesoporous particles for controlled α-linolenic acid delivery to stimulate GLP-1 secretion in vitro.

Novel treatment methods for obesity are urgently needed due to the increasing global severity of the problem. Gastrointestinal hormones, such as GLP-1 and PYY, are secreted by the enteroendocrine cells, playing a critical role in regulating food intake. Digested nutrients trigger the secretion of these hormones, which have a very short half-life. α-Linolenic acid (αLA) has been shown to stimulate GLP-1 secretion, however, chemical instability and fast uptake in the small intestine hinder its use in body weight management. We developed a novel delivery system based on inorganic mesoporous particles for αLA to increase secretion of gastrointestinal peptides. αLA was loaded to thermally hydrocarbonized porous silicon particles (THCPSi). 47.9 ±â€¯3.84% and 30.7 ±â€¯2.86% of αLA was released during 6 h from 3.0% and 9.2% loading degree (w/w) samples in vitro, respectively. Native αLA (50 µM) significantly increased GLP-1 secretion from enteroendocrine STC-1 and GLUTag cell lines. αLA loaded THCPSi significantly and dose dependently stimulated GLP-1 secretion from STC-1 cells, whereas empty particles did not. We demonstrated in vitro that THCPSi particles have the potential to be used as a controlled delivery system for nutrients such as αLA, increasing GLP-1 secretion. Our results justify further in vivo investigations.

Elevated serum S-100ß in patients with septic shock is associated with delirium.

BACKGROUND: A high prevalence of delirium is observed in sepsis, yet specific markers for this brain dysfunction in sedated patients are still lacking. Cytoplasmic low molecular weight calcium-binding protein, S-100ß, is a commonly used nonspecific marker for brain injury. Here, we evaluated whether delirium is associated with increases in S-100ß levels. METHODS: This observational study included 22 patients with septic shock. Delirium was assessed by CAM-ICU and blood samples were obtained to measure inflammatory (CRP, PCT, IL-6, IL-17, TNF-α) and cerebral biomarkers (S-100ß, NSE, HAB42, SUBP). Patients were categorized according to the presence of delirium. RESULTS: Delirium was present in 10/22 of the patients (45.5%). Serum S-100ß levels were above the laboratory cutoff value of 0.15 µg/L in 13/22 (59.1%) of the patients. The odds ratio for risk of developing delirium in cases with an S-100ß >0.15 µg/L was 18.0 (95%CI, 1.7-196.3, P = 0.011). Patients with delirium had higher plasma levels of IL-6 compared to those without; 138.3 pg/mL [28.0-296.7] vs 53.6 pg/mL [109.3-505, P = 0.050]. There was a positive correlation between S100 ß and IL-6 levels (r = 0.489, P = 0.021). Delirium patients had higher SOFA scores; 10 [5-9] vs 7[8-10.5], P = 0.036. CONCLUSIONS: Delirium in septic shock was associated with an elevated protein S-100ß when using a laboratory cutoff value of 0.15 µg/L and with more severe organ dysfunction during the ICU stay.

Retinal arterial blood flow and retinal changes in patients with sepsis: preliminary study using fluorescein angiography.

BACKGROUND: Although tissue perfusion is often decreased in patients with sepsis, the relationship between macrohemodynamics and microcirculatory blood flow is poorly understood. We hypothesized that alterations in retinal blood flow visualized by angiography may be related to macrohemodynamics, inflammatory mediators, and retinal microcirculatory changes. METHODS: Retinal fluorescein angiography was performed twice during the first 5 days in the intensive care unit to observe retinal abnormalities in patients with sepsis. Retinal changes were documented by hyperfluorescence angiography; retinal blood flow was measured as retinal arterial filling time (RAFT); and intraocular pressure was determined. In the analyses, we used the RAFT measured from the eye with worse microvascular retinal changes. Blood samples for inflammation and cerebral biomarkers were collected, and macrohemodynamics were monitored. RAFT was categorized as prolonged if it was more than 8.3 seconds. RESULTS: Of 31 patients, 29 (93%) were in septic shock, 30 (97%) required mechanical ventilation, 22 (71%) developed delirium, and 16 (51.6%) had retinal angiopathies, 75% of which were bilateral. Patients with prolonged RAFT had a lower cardiac index before (2.1 L/kg/m2 vs. 3.1 L/kg/m2, P = 0.042) and during angiography (2.1 L/kg/m2 vs. 2.6 L/kg/m2, P = 0.039). They more frequently had retinal changes (81% vs. 20%, P = 0.001) and higher intraocular pressure (18 mmHg vs. 14 mmHg, P = 0.031). Patients with prolonged RAFT had lower C-reactive protein (139 mg/L vs. 254 mg/L, P = 0.011) and interleukin-6 (39 pg/ml vs. 101 pg/ml, P < 0.001) than those with shorter RAFT. CONCLUSIONS: Retinal angiopathic changes were more frequent and cardiac index was lower in patients with prolonged RAFT, whereas patients with shorter filling times had higher levels of inflammatory markers.

The effects of group and single housing and automated animal monitoring on urinary corticosterone levels in male C57BL/6 mice.

Mice are used extensively in physiological research. Automated home-cage systems have been developed to study single-housed animals. Increased stress by different housing conditions might affect greatly the results when investigating metabolic responses. Urinary corticosteroid concentration is considered as a stress marker. The aim of the study was to compare the effects of different housing conditions and an automated home-cage system with indirect calorimetry located in an environmental chamber on corticosterone levels in mice. Male mice were housed in different conditions and in automated home-cage system to evaluate the effects of housing and measuring conditions on urine corticosterone levels. Corticosterone levels in single-housed mice in the laboratory animal center were consistently lower compared with the group-housed mice. Single-housed mice in a separate, small animal unit showed a rise in their corticosterone levels a day after they were separated to their individual cages, which decreased during the following 2 days. The corticosterone levels of group-housed mice in the same unit were increased during the first 7 days and then decreased. On day 7, the corticosterone concentrations of group-housed mice were significantly higher compared with that of single-housed mice, including the metabolic measurement protocol. In conclusion, single housing caused less stress when compared with group-housed mice. In addition, the urine corticosterone levels were decreased in single-housed mice before the metabolic measurement started. Thus, stress does not affect the results when utilizing the automated system for measuring metabolic parameters like food and water intake and calorimetry.

Antidiabetic effect of green rooibos (Aspalathus linearis) extract in cultured cells and type 2 diabetic model KK-A(y) mice.

Previous studies have demonstrated antidiabetic effects for rooibos (Aspalathus linearis) and aspalathin (ASP), one of its main polyphenols. Rooibos, an endemic plant of South Africa, is well-known for its use as herbal tea. Green ('unfermented') rooibos has been shown to contain more ASP than 'fermented' rooibos tea, currently the major product. In the present study, we investigated the antidiabetic effect of green rooibos extract (GRE) through studies on glucose uptake in L6 myotubes and on pancreatic ß-cell protective ability from reactive oxygen species (ROS) in RIN-5F cells. Its in vivo effect was also examined using obese diabetic KK-A(y) mice. GRE increased glucose uptake under insulin absent condition and induced phosphorylation of 5'-adenosine monophosphate-activated protein kinase (AMPK) in L6 myotubes as previously demonstrated for ASP. In addition to AMPK, GRE also promoted phosphorylation of Akt, another promoter of glucose transporter 4 (GLUT4) translocation, in L6 myotubes unlike ASP, suggesting an involvement of GRE component(s) other than ASP in Akt phosphorylation. Promotion of GLUT4 translocation to the plasma membrane by GRE in L6 myotubes was demonstrated by Western blotting analysis. GRE suppressed the advanced glycation end products (AGEs)-induced increase in ROS levels in RIN-5F pancreatic ß-cells. Subchronic feeding with GRE suppressed the increase in fasting blood glucose levels in type 2 diabetic model KK-A(y) mice. These in vitro and in vivo results strongly suggest that GRE has antidiabetic potential through multiple modes of action.