Microfluidic-enabled quantitative measurements of insulin release dynamics from single islets of Langerhans in response to 5-palmitic acid hydroxy stearic acid

We have studied the influence of nitric oxide (NO) and carbon monoxide (CO), putative messenger molecules in the brain as well as in the islets of Langerhans, on glucose-stimulated insulin secretion and on the activities of the acid α-glucoside hydrolases, enzymes which we previously have shown to be implicated in the insulin release process. We have shown here that exogenous NO gas inhibits, while CO gas amplifies glucose-stimulated insulin secretion in intact mouse islets concomitant with a marked inhibition (NO) and a marked activation (CO) of the activities of the lysosomal/vacuolar enzymes acid glucan-1,4-α-glucosidase and acid α-glucosidase (acid α-glucoside hydrolases). Furthermore, CO dose-dependently potentiated glucose-stimulated insulin secretion in the range 0.1–1000 μM. In intact islets, the heme oxygenase substrate hemin markedly amplified glucose-stimulated insulin release, an effect which was accompanied by an increased activity of the acid α-glucoside hydrolases. These effects were partially suppressed by the guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one. Hemin also inhibited inducible NO synthase (iNOS)-derived NO production probably through a direct effect of CO on the NOS enzyme. Further, exogenous CO raised the content of both cGMP and cAMP in parallel with a marked amplification of glucose-stimulated insulin release, while exogenous NO suppressed insulin release and cAMP, leaving cGMP unaffected. Emiglitate, a selective inhibitor of α-glucoside hydrolase activities, was able to markedly inhibit the stimulatory effect of exogenous CO on both glucose-stimulated insulin secretion and the activityof acid glucan-1,4-α-glucosidase and acid α-glucosidase, while no appreciable effect on the activities of other lysosomal enzyme activities measured was found. We propose that CO and NO, both produced in significant quantities in the islets of Langerhans, have interacting regulatory roles on glucose-stimulated insulin secretion. This regulation is, at least in part, transduced through the activity of cGMP and the lysosomal/vacuolar system and the associated acid α-glucoside hydrolases, but probably also through a direct effect on the cAMP system.

Download Full-text

Fatty Acid Esters of Hydroxy Fatty Acids (FAHFAs) Are Associated With Diet, BMI, and Age

Frontiers in Nutrition ◽

10.3389/fnut.2021.691401 ◽

2021 ◽

Vol 8 ◽

Author(s):

Teresa Kellerer ◽

Karin Kleigrewe ◽

Beate Brandl ◽

Thomas Hofmann ◽

Hans Hauner ◽

...

Keyword(s):

Fatty Acids ◽

Weight Loss ◽

Fatty Acid ◽

Stearic Acid ◽

Palmitic Acid ◽

Fatty Acid Esters ◽

Obese Patients ◽

Hydroxy Stearic Acid ◽

Diabetic Status ◽

Acid Esters

Background: Fatty acid esters of hydroxy fatty acids (FAHFAs) are a group of fatty acids with potential anti-inflammatory and anti-diabetic effects. The blood levels of FAHFAs and their regulation in humans have hardly been studied.Objective: We aimed to investigate serum FAHFA levels in well-characterized human cohorts, to evaluate associations with age, sex, BMI, weight loss, diabetic status, and diet.Methods: We analyzed levels of stearic-acid-9-hydroxy-stearic-acid (9-SAHSA), oleic-acid-9-hydroxy-stearic-acid (9-OAHSA) and palmitic-acid-9-hydroxy-palmitic-acid (9-PAHPA) as well as different palmitic acid-hydroxy-stearic-acids (PAHSAs) by HPLC-MS/MS with the use of an internal standard in various cohorts: A cohort of different age groups (18–25y; 40–65y; 75–85y; Σn = 60); severely obese patients undergoing bariatric surgery and non-obese controls (Σn = 36); obese patients with and without diabetes (Σn = 20); vegetarians/vegans (n = 10) and omnivores (n = 9); and young men before and after acute overfeeding with saturated fatty acids (SFA) (n = 15).Results: Omnivores had substantially higher FAHFA levels than vegetarians/vegans [median (25th percentile; 75th percentile) tFAHFAs = 12.82 (7.57; 14.86) vs. 5.86 (5.10; 6.71) nmol/L; P < 0.05]. Dietary overfeeding by supplementation of SFAs caused a significant increase within 1 week [median tFAHFAs = 4.31 (3.31; 5.27) vs. 6.96 (6.50; 7.76) nmol/L; P < 0.001]. Moreover, obese patients had lower FAHFA levels than non-obese controls [median tFAHFAs = 3.24 (2.80; 4.30) vs. 5.22 (4.18; 7.46) nmol/L; P < 0.01] and surgery-induced weight loss increased 9-OAHSA level while other FAHFAs were not affected. Furthermore, significant differences in some FAHFA levels were found between adolescents and adults or elderly, while no differences between sexes and between diabetic and non-diabetic individuals were detected.Conclusions: FAHFA serum levels are strongly affected by high SFA intake and reduced in severe obesity. Age also may influence FAHFA levels, whereas there was no detectable relation with sex and diabetic status. The physiological role of FAHFAs in humans remains to be better elucidated.Trial Registration: All studies referring to these analyses were registered in the German Clinical Trial Register (https://www.drks.de/drks_web/) with the numbers DRKS00009008, DRKS00010133, DRKS00006211, and DRKS00009797.

Download Full-text

Regulation of insulin secretion from islets of Langerhans rendered permeable by electric discharge

Biochemical Journal ◽

10.1042/bj2060081 ◽

1982 ◽

Vol 206 (1) ◽

pp. 81-87 ◽

Cited By ~ 67

Author(s):

M. Adel Yaseen ◽

Kevin C. Pedley ◽

Simon L. Howell

Keyword(s):

Insulin Secretion ◽

B Cells ◽

Insulin Release ◽

Islets Of Langerhans ◽

Electric Discharge ◽

Significant Inhibition ◽

Marker Enzyme ◽

Ultrastructural Studies ◽

Isolated Islets Of Langerhans ◽

Vinblastine Sulphate

1. High-voltage electric discharge has been used to increase the permeability of B-cells of isolated islets of Langerhans to facilitate studies of the effects of normally impermeable substances on insulin secretion. 2. The application of an intense electric field increased the [14C]sucrose space of the islets from 37.8±3.1% to 86.2±5.2% of their total volume as assessed by 3H2O content. The cells remained permeable for at least 40min. 3. Ultrastructural studies showed no deleterious changes in the structure of the B-cells after discharge. 4. Insulin secretion from normal islets was unaffected by increasing the medium [Ca2+] from 10nm to 10μm. In the islets that had been rendered permeable by discharge, insulin secretion was significantly increased under these conditions, without any alteration in the release of lactate dehydrogenase, a cytoplasmic marker enzyme. 5. Studies of the dynamics of insulin release during perifusion showed that the response to increased (10μm) Ca2+ concentration was rapid and sustained over a period of at least 13min. 6. Secretion responses to Ca2+ in perifusion established that maximum release in permeabilized islets occurs at approx. 1μm-Ca2+ and half-maximum release occurs at approx. 0.6μm-Ca2+. 7. The study of the effect of agents that interfere with the microtubular microfilamentous system in B-cells using a perifusion system revealed that cytochalasin B caused a considerable increase, whereas vinblastine sulphate caused a significant inhibition, in insulin release in response to 1μm-Ca2+. 8. This technique should facilitate the study of the role of normally impermeable ions and metabolic intermediates in the regulation of insulin secretion.

Download Full-text

Potassium ions and the secretion of insulin by islets of Langerhans incubated in vitro

Biochemical Journal ◽

10.1042/bj1080017 ◽

1968 ◽

Vol 108 (1) ◽

pp. 17-24 ◽

Cited By ~ 185

Author(s):

S. L. Howell ◽

K W Taylor

Keyword(s):

Insulin Secretion ◽

Insulin Release ◽

Islets Of Langerhans ◽

Potassium Ions ◽

Collagenase Digestion ◽

Islet Tissue ◽

Rabbit Pancreas ◽

K Concentration

1. A method was devised for the isolation of islets of Langerhans from rabbit pancreas by collagenase digestion in order to study the influx and efflux of K+ in islets during insulin secretion. 2. Glucose-induced insulin release was accompanied by an increased rate of uptake of 42K+ by the islets of Langerhans, though this was not the case for secretion in response to tolbutamide. Ouabain significantly inhibited the uptake of 42K+ by islet tissue. 3. No significant increase in the rate of efflux of 42K+ was demonstrated during active insulin secretion. 4. Slices of rabbit pancreas were incubated in media of different K+ content, and rates of insulin release were determined. Alteration of the K+ concentration of the medium between 3 and 8mm had no effect on the rate of insulin release by pancreas slices. However, decrease of the K+ concentration to 1mm resulted in inhibition of secretion in response to both glucose and to tolbutamide. Conversely, an increase in K+ concentration increased rates of insulin release in response to both these stimuli. 5. It is concluded that, though unphysiological concentrations of K+ may influence the secretion of insulin, fluxes of K+ in the islets do not appear to be important in the initiation of insulin secretion.

Download Full-text

A species difference in nucleoside phosphorylase activity and inosine-stimulated insulin secretion in isolated islets of Langerhans

Biochemical Journal ◽

10.1042/bj1680591 ◽

1977 ◽

Vol 168 (3) ◽

pp. 591-593 ◽

Cited By ~ 6

Author(s):

I L Campbell ◽

K W Taylor

Keyword(s):

Insulin Secretion ◽

Insulin Release ◽

Islets Of Langerhans ◽

Species Differences ◽

Species Difference ◽

Isolated Islets ◽

Phosphorylase Activity ◽

Nucleoside Phosphorylase ◽

Isolated Islets Of Langerhans

Inosine is a potent simulant of insulin release from rat but not from rabbit islets of Langerhans. Further investigation showed that nucleoside phosphorylase activity is exceptionally low in rabbit islets. The ability of inosine to promote insulin release seems to be related to islet nucleoside phosphorylase activity, which can display marked species differences.

Download Full-text

Palmitic acid increase levels of pancreatic duodenal homeobox-1 and p38/stress-activated protein kinase in islets from rats maintained on a low protein diet

British Journal Of Nutrition ◽

10.1017/bjn20061950 ◽

2006 ◽

Vol 96 (6) ◽

pp. 1006-1012 ◽

Cited By ~ 3

Author(s):

Vanessa C. Arantes ◽

Marise A. B. Reis ◽

Márcia Q. Latorraca ◽

Fabiano Ferreira ◽

Luiz Fabrízio Stoppiglia ◽

...

Keyword(s):

Insulin Secretion ◽

Protein Kinase ◽

Palmitic Acid ◽

Insulin Release ◽

Culture Medium ◽

Cell Physiology ◽

Low Protein ◽

Severe Reduction ◽

Insulin Mrna ◽

And Control

A severe reduction in insulin release in response to glucose is consistently noticed in protein-deprived rats and is attributed partly to the chronic exposure to elevated levels of NEFA. Since the pancreatic and duodenal transcription factor homeobox 1 (PDX-1) is important for the maintenance of β-cell physiology, and since PDX-1 expression is altered in the islets of rats fed a low protein (LP) diet and that rats show high NEFA levels, we assessed PDX-1 and insulin mRNA expression, as well as PDX-1 and p38/stress activated protein kinase 2 (SAPK2) protein expression, in islets from young rats fed low (6 %) or normal (17 %; control) protein diets and maintained for 48 h in culture medium containing 5·6 mmol/l glucose, with or without 0·6 mmol/l palmitic acid. We also measured glucose-induced insulin secretion and glucose metabolism. Insulin secretion by isolated islets in response to 16·7 mmol/l glucose was reduced in LP compared with control rats. In the presence of NEFA, there was an increase in insulin secretion in both groups. At 2·8 mmol/l glucose, the metabolism of this sugar was reduced in LP islets, regardless of the presence of this fatty acid. However, when challenged with 16·7 mmol/l glucose, LP and control islets showed a severe reduction in glucose oxidation in the presence of NEFA. The PDX-1 and insulin mRNA were significantly higher when NEFA was added to the culture medium in both groups of islets. The effect of palmitic acid on PDX-1 and p38/SAPK2 protein levels was similar in LP and control islets, but the increase was much more evident in LP islets. These results demonstrate the complex interrelationship between nutrients in the control of insulin release and support the view that fatty acids play an important role in glucose homeostasis by affecting molecular mechanisms and stimulus/secretion coupling pathways.

Download Full-text

Acute effects of fatty acids on insulin secretion from rat and human islets of Langerhans

Journal of Endocrinology ◽

10.1677/joe.0.1730073 ◽

2002 ◽

Vol 173 (1) ◽

pp. 73-80 ◽

Cited By ~ 90

Author(s):

C Gravena ◽

PC Mathias ◽

SJ Ashcroft

Keyword(s):

Fatty Acids ◽

Insulin Secretion ◽

Insulin Release ◽

Islets Of Langerhans ◽

Saturated Fatty Acids ◽

Human Islets ◽

Dependent Manner ◽

Acute Effects ◽

Rat Islets ◽

Human Islets Of Langerhans

Fatty acids have both stimulatory and inhibitory effects on insulin secretion. Long-term exposure to fatty acids results in impaired insulin secretion whilst acute exposure has generally been found to enhance insulin release. However, there are conflicting data in the literature as to the relative efficacy of various fatty acids and on the glucose dependency of the stimulatory effect. Moreover, there is little information on the responses of human islets in vitro to fatty acids. We have therefore studied the acute effects of a range of fatty acids on insulin secretion from rat and human islets of Langerhans at different glucose concentrations. Fatty acids (0.5 mM) acutely stimulated insulin release from rat islets of Langerhans in static incubations in a glucose-dependent manner. The greatest effect was seen at high glucose concentration (16.7 mM) and little or no response was elicited at 3.3 or 8.7 mM glucose. Long-chain fatty acids (palmitate and stearate) were more effective than medium-chain (octanoate). Saturated fatty acids (palmitate, stearate) were more effective than unsaturated (palmitoleate, linoleate, elaidate). Stimulation of insulin secretion by fatty acids was also studied in perifused rat islets. No effects were observed at 3.3 mM glucose but fatty acids markedly potentiated the effect of 16.7 mM glucose. The combination of fatty acid plus glucose was less effective when islets had been first challenged with glucose alone. The insulin secretory responses to fatty acids of human islets in static incubations were similar to those of rat islets. In order to examine whether the responses to glucose and to fatty acids could be varied independently we used an animal model in which lactating rats are fed a low-protein diet during early lactation. Islets from rats whose mothers had been malnourished during lactation were still able to respond effectively to fatty acids despite a lowered secretory response to glucose. These data emphasise the complex interrelationships between nutrients in the control of insulin release and support the view that fatty acids play an important role in glucose homeostasis during undernutrition.

Download Full-text

Acute and long-term effects of metformin on the function and insulin secretory responsiveness of clonal β-cells

Biological Chemistry ◽

10.1515/bc.2010.139 ◽

2010 ◽

Vol 391 (12) ◽

Cited By ~ 5

Author(s):

Joan M. McKiney ◽

Nigel Irwin ◽

Peter R. Flatt ◽

Clifford J. Bailey ◽

Neville H. McClenaghan

Keyword(s):

Insulin Secretion ◽

Cell Viability ◽

Palmitic Acid ◽

Insulin Release ◽

Prolonged Exposure ◽

Long Term Effects ◽

Β Cell ◽

Beneficial Effects ◽

Intracellular Ca ◽

Glucose Stimulated Insulin Secretion

Abstract Functional effects of acute and prolonged (48 h) exposure to the biguanide drug metformin were examined in the clonal pancreatic β-cell line, BRIN-BD11. Effects of metformin on prolonged exposure to excessive increased concentrations of glucose and palmitic acid were also assessed. In acute 20-min incubations, 12.5–50 μm metformin did not alter basal (1.1 mm glucose) or glucose-stimulated (16.7 mm glucose) insulin secretion. However, higher concentrations of metformin (100–1000 μm) increased (1.3–1.5-fold; p<0.001) insulin release at basal glucose concentrations, but had no effect on glucose-stimulated insulin secretion. There were no apparent acute effects of metformin on intracellular Ca2+ concentrations, but metformin enhanced (p<0.05 to p<0.01) the acute insulinotropic actions of GIP and GLP-1. Exposure for 48 h to 200 μm metformin improved aspects of β-cell insulin secretory function, whereas these benefits were lost at 1 mm metformin. Prolonged glucotoxic and lipotoxic conditions impaired β-cell viability and insulin release in response to glucose and to a broad range of insulin secretagogues. Concomitant culture with 200 μm metformin partially reversed many of the adverse effects of prolonged glucotoxic conditions. However, there were no beneficial effects of metformin under prolonged culture with elevated concentrations of palmitic acid. The results suggest that metformin exerts direct effects on β-cell viability, function and survival that could contribute to the use of this agent in the treatment of type 2 diabetes.

Download Full-text

Cyclic AMP-dependent protein phosphorylation and insulin secretion in intact islets of Langerhans

Biochemical Journal ◽

10.1042/bj2180087 ◽

1984 ◽

Vol 218 (1) ◽

pp. 87-99 ◽

Cited By ~ 31

Author(s):

M R Christie ◽

S J H Ashcroft

Keyword(s):

Insulin Secretion ◽

Cyclic Amp ◽

Protein Phosphorylation ◽

Cholera Toxin ◽

Insulin Release ◽

Islets Of Langerhans ◽

Sodium Dodecyl ◽

Major Effect ◽

Maximum Effect ◽

Calmodulin Antagonist

Effects on insulin release, cyclic AMP content and protein phosphorylation of agents modifying cyclic AMP levels have been tested in intact rat islets of Langerhans. Insulin release induced by glucose was potentiated by dibutyryl cyclic AMP, glucagon, cholera toxin and 3-isobutyl-1-methylxanthine (IBMX); the calmodulin antagonist trifluoperazine reversed these potentiatory effects. Inhibition by trifluoperazine of IBMX-potentiated release was, however, confined to concentrations of IBMX below 50 microM; higher concentrations, up to 1 mM, were resistant to inhibition by trifluoperazine. IBMX-potentiated insulin release was also inhibited by 2-deoxyadenosine, an inhibitor of adenylate cyclase. In the absence of glucose, IBMX at concentrations up to 1 mM did not stimulate insulin release and in the presence of 3.3 mM-glucose IBMX was effective only at a concentration of 1 mM; under the latter conditions trifluoperazine again did not inhibit insulin secretion. The maximum effect on insulin release was achieved with 25 microM-IBMX. Islet [cyclic AMP] was increased by IBMX, with the maximum rise occurring with 100 microM-IBMX. The increase in [cyclic AMP] elicited by IBMX was more rapid than that induced by cholera toxin. Trifluoperazine did not significantly affect islet cyclic AMP levels under any of the conditions tested. When islets were incubated with [32P]Pi, radioactivity was incorporated into islet ATP predominantly in the gamma-position. The rate of equilibration of label was dependent on medium Pi and glucose concentration and at optimal concentrations of these 100% equilibration of internal [32P]ATP with external [32P]Pi required a period of 3h. Radioactivity was incorporated into islet protein and, in response to an increase in islet [cyclic AMP], the major effect was on a protein of Mr 15 000 on sodium dodecyl sulphate/polyacrylamide gels. The extent of phosphorylation of the Mr-15 000 protein was correlated with the level of cyclic AMP: phosphorylation in response to IBMX was inhibited by 2-deoxyadenosine but not by trifluoperazine. Fractionation of islets suggested that the Mr-15 000 protein was of nuclear origin: the protein co-migrated with histone H3 on acetic acid/urea/Triton gels. In the islet cytosol a number of proteins were phosphorylated in response to elevation of islet [cyclic AMP]: the major species had Mr values of 18 000, 25 000, 34 000, 38 000 and 48 000. Culture of islets with IBMX increased the rate of [3H]-thymidine incorporation.(ABSTRACT TRUNCATED AT 400 WORDS)

Download Full-text