Lipid Infusion Research Articles

A novel nutritional approach to infants and children with congenital diarrhea due to homozygous DGAT1 mutations.

Diacylglycerol acyltransferase (DGAT) catalyzes the final step in triglyceride synthesis. DGAT1 is expressed in human enterocytes and is essential for fat absorption. Homozygous DGAT1 deficiency often presents with severe diarrhea and protein-losing enteropathy (PLE) in the 1st weeks of life. Because severe restriction of fat intake controls diarrhea and decreases PLE, total parenteral nutrition (TPN) was the initial standard therapy in infants and children. We present tertiary center experience managing infants and children with DGAT1 deficiency resulting in the development of a nutritional approach that minimizes the use of TPN. From 2014 to 2020, 12 infants with DGAT1 deficiency were treated. Stool output, growth, and development, as well as essential fatty acid status, were monitored. This retrospective experience formed the basis for treatment recommendations, which include an ultralow fat formula with intermittent peripheral intravenous lipid infusions during the 1st year of life. All patients with prolonged intestinal fat exposure had PLE, which resolved when treated with the nutrition protocol. Essential fatty acid status as measured by triene:tetraene ratios normalized in all treated patients. Over time, early genetic diagnosis and prompt initiation of an ultralow fat diet with peripheral intravenous lipid infusions replaced the need for TPN. Children with DGAT1 deficiency respond to dietary restriction of lipids. Management with a novel nutritional approach provides effective treatment for infants with DGAT1 deficiency, treats diarrhea and PLE, promotes growth and development, avoids TPN dependency, and decreases the potential for essential fatty acid deficiency.

Short-term parenteral infusions with high-osmolality amino acid solutions can be safely administered through peripheral catheters in dogs treated for hypoaminoacidemia-related conditions.

To compare complications between central and peripheral administration of high-osmolarity (approx 700 to 1,000 mOsm/L) amino acid (± lipid) infusions. 18 client-owned dogs diagnosed with aminoaciduric canine hypoaminoacidemic hepatopathy syndrome or superficial necrolytic dermatitis receiving parenteral amino acid ± lipid infusions. In this retrospective case series, medical records were reviewed for administration route (central vs peripheral), catheter details and infusion characteristics (product osmolarity, concurrent lipid administration, infusion volume, duration, and rate), and complications for each infusion. 18 dogs received 277 infusions (median, 8.5; range, 1 to 84). Effective infusion osmolarities were 683 mOsm/L in 22% of infusions, 791 mOsm/L in 8%, 802 mOsm/L in 2%, 837 mOsm/L in 45%, and 998 mOsm/L in 23% (65% peripheral, 35% central). Most (n = 230 [83%]) infusions were given peripherally. The osmolarities of solutions administered by each route (P = .53), the infusion rate indexed to body weight (P = .17), or the lipid infusion rates indexed to body weight (P = .89) did not differ. One dog suffered 2 complications in 63 infusions-1 mild, 1 severe-both occurring with peripheral infusions. Thus, the overall complication rate was 2 of 277 (0.9%) infusions. Short-term peripherally administered amino acid ± lipid infusions < 1,000 mOsm/L confer little risk compared to centrally administered infusions. Additional studies are needed to determine the safety of infusions with longer durations. Due to the relative ease of peripheral catheterization, clinicians should consider this route for medically managing aminoaciduric canine hypoaminoacidemic hepatopathy syndrome and superficial necrolytic dermatitis in dogs.

Effects of ondansetron on symptoms during a gastric emptying study and enteral lipid challenge and on daily symptoms in diabetic gastroenteropathy.

This study compared the effects of ondansetron and placebo in patients with diabetes mellitus and symptoms of dyspepsia (diabetic gastroenteropathy [DGE]). We performed a randomized, double-blinded, placebo-controlled study of ondansetron tablets (8 mg) three times daily for 4 weeks in DGE patients. Symptoms were assessed with the Gastroparesis Cardinal Symptom Index daily diaries. Gastric emptying (GE) of solids (scintigraphy) and duodenal lipid infusions (300 kcal over 2 h) were each assessed twice, with placebo and ondansetron. Drug effects on GE, symptoms during the GE study and during lipid infusion, and daily symptoms were analyzed. Of 41 patients, 37 completed both GE studies and one completed 1; 31 completed both lipid infusions and four only placebo; and all 35 randomized patients completed 4 weeks of treatment. Compared to placebo, ondansetron reduced the severity of fullness (p = 0.02) and belching (p = 0.049) during lipid infusion but did not affect GE T1/2. Both ondansetron and placebo improved daily symptoms versus the baseline period (p < 0.05), but the differences were not significant. In the analysis of covariance of daily symptoms during the treatment period, the interaction term between treatment and the acute effect of ondansetron on symptoms during lipid challenge was significant (p = .024). Ondansetron significantly reduced fullness during enteral lipid infusion in patients with DGE. Overall, ondansetron did not improve daily symptoms versus placebo. But patients in whom ondansetron improved symptoms during enteral lipid challenge were perhaps more likely to experience symptom relief during daily treatment.

Innovative assessment of lipid-induced oxidative stress and inflammation in harvested human endothelial cells.

Studying acute changes in vascular endothelial cells in humans is challenging. We studied ten African American women and used the J-wire technique to isolate vein endothelial cells before and after a four-hour lipid and heparin infusion. Dynamic changes in lipid-induced oxidative stress and inflammatory markers were measured with fluorescence-activated cell sorting. We used the surface markers CD31 and CD144 to identify human endothelial cells. Peripheral blood mononuclear cells isolated from blood were used as a negative control. The participants received galantamine (16 mg/day) for 3 months. We previously demonstrated that galantamine treatment effectively suppresses lipid-induced oxidative stress and inflammation. In this study, we infused lipids to evaluate its potential to increase the activation of endothelial cells, as assessed by the levels of CD54+ endothelial cells and expression of Growth arrest-specific 6 compared to the baseline sample. Further, we aimed to investigate whether lipid infusion led to increased expression of the oxidative stress markers IsoLGs and nitrotyrosine in endothelial cells. This approach will expedite the invivo identification of novel pathways linked with endothelial cell dysfunction induced by oxidative stress and inflammatory cytokines. This study describes an innovative method to harvest and study human endothelial cells and demonstrates the dynamic changes in oxidative stress and inflammatory markers release induced by lipid infusion.

Antioxidant-induced modulation of sympathetic transduction to arterial blood pressure in humans

Purpose: Excess plasma free fatty acids (FAA) promote oxidative stress and an increase in peripheral resistance. Therefore, we tested the hypothesis that excess FAA limits sympathetic control of arterial blood pressure (BP) and that sympathetic control would be restored during co-administration of ascorbic acid, which is an antioxidant with vasodilatory properties. Methods: A 20% IV fat emulsion (Intralipid) was administered for 2 hours to 5 lean, healthy adults with and without co-infusion of ascorbic acid (separate visits) in a double-blinded, crossover study design. Sympathetic control of BP was examined by determining the BP response to individual bursts of muscle sympathetic nerve activity (MSNA) (microneurography). Briefly, beat-to-beat mean arterial pressure (MAP) was measured continuously (finger cuff) and signal-averaged over 15 cardiac cycles following each detected burst of MSNA over a 10-min resting period. Results: In contrast to our hypothesis, no change was observed in sympathetic transduction during lipid infusion (1.5 ± 0.4 vs. 1.4 ± 3 mmHg, P=0.75). However, co-infusion of ascorbic acid significantly increased sympathetic transduction compared with baseline (1.5 ± 0.4 vs. 2.0 ± 3 mmHg, P=0.04), in addition to reducing peripheral resistance (0.73 ± 0.11 vs. 0.53 ± 12 mmHg·min·mL−1, P=0.07). MSNA and MAP were not significantly changed during the 2-hr infusions. Conclusions: These preliminary findings suggest that excess FAA do not modulate sympathetic transduction in lean, healthy adults. However, ascorbic acid infusion reduces peripheral resistance and increases sympathetic transduction, demonstrating an inverse relation between peripheral resistance and sympathetic transduction in healthy adults. Funding and support: R01HL159370-01 (S.W.H.). This work was also supported by a CTSA grant from NCATS awarded to the University of Kansas for Frontiers: University of Kansas Clinical and Translational Science Institute (# UL1TR002366) The contents are solely the responsibility of the authors and do not necessarily represent the offcial views of the NIH or NCATS. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Effects of hypertriglyceridemia with or without NEFA elevation on β-cell function and insulin clearance and sensitivity.

Hypertriglyceridemia is a risk factor for developing type 2 diabetes (T2D) and might contribute to its pathogenesis either directly or through elevation of non-esterified fatty acids (NEFAs). This study aimed at comparing the glucometabolic effects of acute hypertriglyceridemia alone or combined with NEFA elevation in non-diabetic subjects. Twenty-two healthy lean volunteers underwent two 5-h intravenous infusions of either saline or Intralipid, without (n=12) or with heparin (I+H; n=10) to activate the release of NEFAs. Oral glucose tolerance tests (OGTTs) were performed during the last 3h of infusion. Insulin sensitivity, insulin secretion rate (ISR), model-derived β-cell function, and insulin clearance were measured after 2h of lipid infusion and during the OGTTs. In fasting conditions, both lipid infusions increased plasma insulin and ISR and reduced insulin clearance, without affecting plasma glucose and insulin sensitivity. These effects on insulin and ISR were more pronounced for I+H than Intralipid alone. During the OGTT, the lipid infusions markedly impaired glucose tolerance, increased plasma insulin and ISR, and decreased insulin sensitivity and clearance, without significant group differences. Intralipid alone inhibited glucose-stimulated insulin secretion (i.e. β-cell glucose sensitivity) and increased β-cell potentiation, whereas I+H had neutral effects on these β-cell functions. In healthy non-obese subjects, mild acute hypertriglyceridemia directly reduces glucose tolerance, insulin sensitivity and clearance, and has selective and opposite effects on β-cell function that are neutralized by NEFAs. These findings provide new insight into plausible biological signals that generate and sustain insulin resistance and chronic hyperinsulinemia in the development of T2D.

GLUT4 localisation with the plasma membrane is unaffected by an increase in plasma free fatty acid availability

BackgroundInsulin-stimulated glucose uptake into skeletal muscle occurs via translocation of GLUT4 from intracellular storage vesicles to the plasma membrane. Elevated free fatty acid (FFA) availability via a lipid infusion reduces glucose disposal, but this occurs in the absence of impaired proximal insulin signalling. Whether GLUT4 localisation to the plasma membrane is subsequently affected by elevated FFA availability is not known.MethodsTrained (n = 11) and sedentary (n = 10) individuals, matched for age, sex and body mass index, received either a 6 h lipid or glycerol infusion in the setting of a concurrent hyperinsulinaemic-euglycaemic clamp. Sequential muscle biopsies (0, 2 and 6 h) were analysed for GLUT4 membrane localisation and microvesicle size and distribution using immunofluorescence microscopy.ResultsAt baseline, trained individuals had more small GLUT4 spots at the plasma membrane, whereas sedentary individuals had larger GLUT4 spots. GLUT4 localisation with the plasma membrane increased at 2 h (P = 0.04) of the hyperinsulinemic-euglycemic clamp, and remained elevated until 6 h, with no differences between groups or infusion type. The number of GLUT4 spots was unchanged at 2 h of infusion. However, from 2 to 6 h there was a decrease in the number of small GLUT4 spots at the plasma membrane (P = 0.047), with no differences between groups or infusion type.ConclusionGLUT4 localisation with the plasma membrane increases during a hyperinsulinemic-euglycemic clamp, but this is not altered by elevated FFA availability. GLUT4 appears to disperse from small GLUT4 clusters located at the plasma membrane to support glucose uptake during a hyperinsulinaemic-euglycaemic clamp.

Continuous flow local anesthetic wound infusion for post-operative analgesia following kidney transplantation.

Some patients with end stage renal disease are or will become narcotic-dependent. Chronic narcotic use is associated with increased graft loss and mortality following kidney transplantation. We aimed to compare the efficacy of continuous flow local anesthetic wound infusion pumps (CFLAP) with patient controlled analgesia pumps (PCA) in reducing inpatient narcotic consumption in patients undergoing kidney transplantation. In this single-center, retrospective analysis of patients undergoing kidney transplantation, we collected demographic and operative data, peri-operative outcomes, complications, and inpatient oral morphine milligram equivalent (OME) consumption. Four hundred and ninety-eight patients underwent kidney transplantation from 2020 to 2022. 296 (59%) historical control patients received a PCA for postoperative pain control and the next 202 (41%) patients received a CFLAP. Median age [53.5vs. 56.0 years, p=.08] and BMI [29.5vs. 28.9kg/m2, p=.17] were similar. Total OME requirement was lower in the CFLAP group [2.5vs. 34 mg, p<.001]. Wound-related complications were higher in the CFLAP group [5.9%vs. 2.7%, p=.03]. Two (.9%) patients in the CFLAP group experienced cardiac arrhythmia due to local anesthetic toxicity and required lipid infusion. Compared to PCA, CFLAP provided a 93% reduction in OME consumption with a small increase in the wound-related complication rate. The utility of local anesthetic pumps may also be applicable to patients undergoing any unilateral abdominal or pelvic incision.

Principles of the pharmacology of local anesthetics

The development of local anesthetics revolutionized the performance of painful interventions. Local anesthetics have an effect on voltage-gated sodium channels in nerve fibers and modulate the conduction of impulses. With respect to the chemical structure, local anesthetics can be divided into amide and ester types. The structural differences of local anesthetics have an influence on the duration of action, the degradation pathways and specific side effects. Severe adverse events include cardiotoxicity and neurotoxicity. In addition to basic measures, such as the monitoring and securing of vital parameters, lipid infusion represents a treatment option in cases of intoxication. The recent developments of local anesthetics are particularly concerned with the reduction of toxicity and prolonging the duration of action.

Ketogenic propensity is differentially related to lipid-induced hepatic and peripheral insulin resistance.

Determine the ketogenic response (β-hydroxybutyrate, a surrogate of hepatic ketogenesis) to a controlled lipid overload in humans. In total, nineteen young, healthy adults (age: 28.4 ± 1.7 years; BMI: 22.7 ± 0.3 kg/m2 ) received either a 12 h overnight lipid infusion or saline in a randomized, crossover design. Plasma ketones and inflammatory markers were quantified by colorimetric and multiplex assays. Hepatic and peripheral insulin sensitivity was assessed by the hyperinsulinemic-euglycemic clamp. Skeletal muscle biopsies were obtained to quantify gene expression related to ketone body metabolism and inflammation. By design, the lipid overload-induced hepatic (50%, p < 0.001) and peripheral insulin resistance (73%, p < 0.01) in healthy adults. Ketones increased with hyperlipidemia and were subsequently reduced with hyperinsulinemia during the clamp procedure (Saline: Basal = 0.22 mM, Insulin = 0.07 mM; Lipid: Basal = 0.78 mM, Insulin = 0.51 mM; 2-way ANOVA: Lipid p < 0.001, Insulin p < 0.001, Interaction p = 0.07). In the saline control condition, ketones did not correlate with hepatic or peripheral insulin sensitivity. Conversely, in the lipid condition, ketones were positively correlated with hepatic insulin sensitivity (r = 0.59, p < 0.01), but inversely related to peripheral insulin sensitivity (r = -0.64, p < 0.01). Hyperlipidemia increased plasma inflammatory markers, but did not impact skeletal muscle inflammatory gene expression. Gene expression related to ketone and fatty acid metabolism in skeletal muscle increased in response to hyperlipidemia. This work provides important insight into the role of ketones in human health and suggests that ketone body metabolism is altered at the onset of lipid-induced insulin resistance.

Myocardial glucose suppression may interfere with the detection of inflammatory cells with FDG-PET as suggested in a canine model of myocardial infarction

BackgroundAfter myocardial infarction, fibrosis and an ongoing dysregulated inflammatory response have been shown to lead to adverse cardiac remodeling. FDG PET is an imaging modality sensitive to inflammation as long as suppression protocols are observed while gadolinium enhanced MRI can be used to determine extracellular volume (ECV), a measure of fibrosis. In patients, glucose suppression is achieved variously through a high fat diet, fasting and injection of heparin. To emulate this process in canines, a heparin injection and lipid infusion are used, leading to similar fatty acids in the blood. The aim of this study was to examine the effect of glucose suppression on the uptake of FDG in the infarcted myocardial tissue and also on the determination of ECV in both the infarcted tissue and in the myocardium remote to the zone of infarction during a long constant infusion of FDG and Gd-DTPA.ResultsExtracellular volume was affected neither by suppression nor the length of the constant infusion in remote and infarcted tissue. Metabolic rate of glucose in infarcted tissue decreased during and after suppression of glucose uptake by lipid infusion and heparin injection. An increase in fibrosis and inflammatory cells was found in the center of the infarct as compared to remote tissue.ConclusionThe decrease in the metabolic rate of glucose in the infarcted tissue suggests that inflammatory cells may be affected by glucose suppression through heparin injection and lipid infusion.

Principles of the pharmacology of local anesthetics

The development of local anesthetics revolutionized the performance of painful interventions. Local anesthetics have an effect on voltage-gated sodium channels in nerve fibers and modulate the conduction of impulses. With respect to the chemical structure, local anesthetics can be divided into amide and ester types. The structural differences of local anesthetics have an influence on the duration of action, the degradation pathways and specific side effects. Severe adverse events include cardiotoxicity and neurotoxicity. In addition to basic measures, such as the monitoring and securing of vital parameters, lipid infusion represents a treatment option in cases of intoxication. The recent developments of local anesthetics are particularly concerned with the reduction of toxicity and prolonging the duration of action.

Effect of C-reactive protein deficiency on insulin resistance reversal in rats with polycystic ovary syndrome through augmented leptin action

BackgroundC-reactive protein(CRP), is an inflammatory marker that weaken leptin bioavailability and insulin sensitivity to disturb energy and glucose metabolism. Polycystic ovary syndrome (PCOS) exhibit a metabolic component consisting of higher plasma CRP levels, hyperinsulinemic and hyperleptinemia. The ability of leptin to regulation of hepatic glucose production (HGP) in the absence of CRP in PCOS remain unknown.MethodsDehydroepiandrosterone (DHEA) was used to induce PCOS in rats. We assessed the effects of CRP gene knockout in PCOS model rats on body weight, energy expenditure glucose metabolism and insulin sensitivity. We conducted experiments involving the administration of leptin to both the peripheral and central systems in PCOS model rats with CRP knockout, and studied the effects on changes in glucose kinetics during hyperinsulinemic-euglycemic clamps.ResultsIn female PCOS rats, the lack of CRP resulted in decreased leptin resistance and weight gain, increased energy expenditure, and improved insulin sensitivity. Additionally, the deletion of the CRP gene strengthened the HGP-lowering effects of leptin when administered peripherally or centrally. This effect was accompanied by a decrease in the expression of hepatic gluconeogenic enzymes and an increase in hepatic insulin signaling. Finally, inhibition of glucose production was also enhanced for central leptin administration during lipid infusion in PCOS rats.ConclusionsOur findings highlight the therapeutic potential of targeting CRP to restore glucose homeostasis and insulin sensitivity for leptin in PCOS.

Downregulated APOD and FCGR2A correlates with immune infiltration and lipid-induced symptoms of irritable bowel syndrome

Fat intake is among the most significant triggers for symptom development in patients with irritable bowel syndrome (IBS). Nevertheless, long-term restriction in fatty foods ingestion may lead to nutritional inadequacies. This study aimed to identify the crucial genes involved in lipid-induced gastrointestinal symptoms, contributing to helping IBS patients regulate fat. The clinical characteristics of the subjects were collected by questionnaire investigation and analyzed using multivariate logistic regression. Differentially expressed genes (DEG) and signaling pathways were analyzed by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. ImmuInfiltration and CIBERSORT packages evaluated small intestine immune cell infiltration. Random forest and SVM-RFE algorithms were used to select hub genes. A receiver operating characteristic curve was used to access the diagnostic significance of each hub gene. Gene Set Enrichment Analysis (GSEA) was performed to identify hub genes’ molecular processes in IBS development after lipid infusion. IBS patients’ risk, severity, and quality of life increased with fat intake. In total, 116 robust DEGs were identified in IBS patients after lipid infusion using the GSE166869 dataset and were mainly clustered in the immune and inflammatory pathways. IBS patients had greater Neutrophils, CD4+ T cells, and M1 Macrophages than healthy controls. Furthermore, infiltration levels of Neutrophils and resting memory CD4+ T cells were inversely related to the expression of hub genes (IGKV1D-43, IGKV1-12, APOD, FCGR2A and IGKV2-29). After lipid infusion, GSEA results of each hub gene indicated the relevance of proinflammatory pathways in IBS pathogenesis. After verification, only APOD and FCGR2A were stably downregulated in small intestinal mucosa and plasma of IBS patients. The area under the curve of APOD combined with FCGR2A expression was 0.9. APOD and FCGR2A may be promising biomarkers for IBS diagnosis and lipid-sensitive IBS patients. Their potential roles in the immune microenvironment of the small intestinal mucosa may provide a vital clue to IBS precision therapy.

Oligofructose improves small intestinal lipid-sensing mechanisms via alterations to the small intestinal microbiota

BackgroundUpper small intestinal dietary lipids activate a gut-brain axis regulating energy homeostasis. The prebiotic, oligofructose (OFS) improves body weight and adiposity during metabolic dysregulation but the exact mechanisms remain unknown. This study examines whether alterations to the small intestinal microbiota following OFS treatment improve small intestinal lipid-sensing to regulate food intake in high fat (HF)-fed rats.ResultsIn rats fed a HF diet for 4 weeks, OFS supplementation decreased food intake and meal size within 2 days, and reduced body weight and adiposity after 6 weeks. Acute (3 day) OFS treatment restored small intestinal lipid-induced satiation during HF-feeding, and was associated with increased small intestinal CD36 expression, portal GLP-1 levels and hindbrain neuronal activation following a small intestinal lipid infusion. Transplant of the small intestinal microbiota from acute OFS treated donors into HF-fed rats also restored lipid-sensing mechanisms to lower food intake. 16S rRNA gene sequencing revealed that both long and short-term OFS altered the small intestinal microbiota, increasing Bifidobacterium relative abundance. Small intestinal administration of Bifidobacterium pseudolongum to HF-fed rats improved small intestinal lipid-sensing to decrease food intake.ConclusionOFS supplementation rapidly modulates the small intestinal gut microbiota, which mediates improvements in small intestinal lipid sensing mechanisms that control food intake to improve energy homeostasis.7qHK-ay1HXaqfvyHrZSPZbVideo

Effect of reduced versus usual lipid emulsion dosing on bilirubin neurotoxicity and neurodevelopmental impairment in extremely preterm infants: study protocol for a randomized controlled trial

BackgroundBilirubin neurotoxicity (BN) occurs in premature infants at lower total serum bilirubin levels than term infants and causes neurodevelopmental impairment. Usual dose lipid infusions in preterm infants may increase free fatty acids sufficiently to cause bilirubin displacement from albumin, increasing passage of unbound bilirubin (UB) into the brain leading to BN and neurodevelopmental impairment not reliably identifiable in infancy. These risks may be influenced by whether cycled or continuous phototherapy is used to control bilirubin levels.ObjectiveTo assess differences in wave V latency measured by brainstem auditory evoked responses (BAER) at 34–36 weeks gestational age in infants born ≤ 750 g or < 27 weeks’ gestational age randomized to receive usual or reduced dose lipid emulsion (half of the usual dose) irrespective of whether cycled or continuous phototherapy is administered.MethodsPilot factorial randomized controlled trial (RCT) of lipid dosing (usual and reduced) with treatment groups balanced between cycled or continuous phototherapy assignment. Eligible infants are born at ≤ 750 g or < 27 weeks’ gestational age enrolled in the NICHD Neonatal Research Network RCT of cycled or continuous phototherapy. Infants will randomize 1:1 to reduced or usual dose lipid assignment during the first 2 weeks after birth and stratified by phototherapy assignment. Free fatty acids and UB will be measured daily using a novel probe. BAER testing will be performed at 34–36 weeks postmenstrual age or prior to discharge. Blinded neurodevelopmental assessments will be performed at 22–26 months. Intention-to-treat analyses will be performed with generalized linear mixed models with lipid dose and phototherapy assignments as random effects covariates, and assessment for interactions. Bayesian analyses will be performed as a secondary analysis.DiscussionPragmatic trials are needed to evaluate whether lipid emulsion dosing modifies the effect of phototherapy on BN. This factorial design presents a unique opportunity to evaluate both therapies and their interaction. This study aims to address basic controversial questions about the relationships between lipid administration, free fatty acids, UB, and BN. Findings suggesting a reduced lipid dose can diminish the risk of BN would support the need for a large multicenter RCT of reduced versus usual lipid dosing.Trial registrationClinical Trials.gov, NCT04584983, Registered 14 October 2020, https://clinicaltrials.gov/ct2/show/NCT04584983Protocol version: Version 3.2 (10/5/2022).

1554-P: Carnosic Acid Protects against Short-Term Lipid-Infusion–Induced Glucose Intolerance in Mice

Background: Obesity and type 2 diabetes (T2D) are associated with elevated plasma free fatty acids (FFA). In vivo exposure to FFAs, such as palmitate, by lipid infusion results in insulin resistance as observed in obesity and T2D. In recent years, compounds found in herbs and plants have attracted attention for prevention and treatment of insulin resistance and T2D. In recent studies by our group, carnosic acid (CA), found in rosemary, increased glucose uptake and attenuated the FFA (palmitate)-induced insulin resistance in muscle cells and adipocytes. In addition, CA caused a robust activation of AMP-activated protein kinase (AMPK). Our present study aimed to examine the effects of CA in short-term FFA-induced glucose intolerance in mice. Material and Methods: C57Bl/6J mice were cannulated in their jugular veins and infused for 48h with ethylpalmitate (EtP, nontoxic method of elevating circulating palmitate because of hydrolysis to palmitate and ethanol by plasma esterases), mimicking elevated FFA levels seen in obesity. In addition, a group of mice were infused with EtP plus 50 mg/kg CA for 48h. Ethanol vehicle with or without CA were two additional control groups. At the end of the infusions, the mice were subjected to a 2 hr hyperglycemic clamp (20 mM glucose) and the glucose infusion rate was measured to assess glucose tolerance. Results: Preliminary data revealed that mice infused with EtP and CA had a higher glucose infusion rate (GIR; mg/kg*min) (66.5±10, mean±SEM) than mice infused with EtP alone (22.7±10). The EtP and CA was comparable to the GIR of ethanol vehicle infused mice (73±9). Future Directions: Further analysis of collected plasma and tissue will be used to assess insulin resistance and beta cell function in vivo and to elucidate the mechanisms of CA alleviation of FFA-induced insulin resistance. Conclusions: Our data indicate that CA has the potential to counteract FFA-induced glucose intolerance in mice. Disclosure N.Tsakiridis: None. F.Vlavcheski: None. E.Tsiani: None. A.Giacca: None.

Effects of subtotal pancreatectomy and long-term glucose and lipid overload on insulin secretion and glucose homeostasis in minipigs.

Nowadays, there are no strong diabetic pig models, yet they are required for various types of diabetes research. Using cutting-edge techniques, we attempted to develop a type 2 diabetic minipig model in this study by combining a partial pancreatectomy (Px) with an energetic overload administered either orally or parenterally. Different groups of minipigs, including Göttingen-like (GL, n = 17) and Ossabaw (O, n = 4), were developed. Prior to and following each intervention, metabolic assessments were conducted. First, the metabolic responses of the Göttingen-like (n = 3) and Ossabaw (n = 4) strains to a 2-month High-Fat, High-Sucrose diet (HFHSD) were compared. Then, other groups of GL minipigs were established: with a single Px (n = 10), a Px combined with a 2-month HFHSD (n = 6), and long-term intraportal glucose and lipid infusions that were either preceded by a Px (n = 4) or not (n = 4). After the 2-month HFHSD, there was no discernible change between the GL and O minipigs. The pancreatectomized group in GL minipigs showed a significantly lower Acute Insulin Response (AIR) (18.3 ± 10.0 IU/mL after Px vs. 34.9 ± 13.7 IU/mL before, p < .0005). In both long-term intraportal infusion groups, an increase in the Insulinogenic (IGI) and Hepatic Insulin Resistance Indexes (HIRI) was found with a decrease in the AIR, especially in the pancreatectomized group (IGI: 4.2 ± 1.9 after vs. 1.5 ± 0.8 before, p < .05; HIRI (×10-5 ): 12.6 ± 7.9 after vs. 3.8 ± 4.3 before, p < .05; AIR: 24.4 ± 13.7 µIU/mL after vs. 43.9 ± 14.5 µIU/mL before, p < .005). Regardless of the group, there was no fasting hyperglycemia. In this study, we used pancreatectomy followed by long-term intraportal glucose and lipid infusions to develop an original minipig model with metabolic syndrome and early signs of glucose intolerance. We reaffirm the pig's usefulness as a preclinical model for the metabolic syndrome but without the fasting hyperglycemia that characterizes diabetes mellitus.

Impaired endothelial function via fatty acids and the potential role of oxidative stress

Purpose: Excess plasma lipids promote oxidative stress and impaired vascular function. Therefore, we tested the hypothesis that a water-soluble antioxidant (ascorbic acid, AA) would attenuate reductions in endothelium-dependent dilation resulting from acutely elevated plasma fatty acids. Methods: A 20% IV fat emulsion (Intralipid) was administered for 2 hours to 8 healthy, middle-aged adults (2 men/6 women) with and without co-infusion of ascorbic acid (separate visits) in a double-blinded, crossover study design. Co-infusion of AA was administered at 0.06g/kg fat free mass in 100 ml saline at 5 mL/min over 20 min (bolus) followed by a drip infusion at 0.02 g/kg fat-free mass in 30 ml saline at 0.33 mL/min over 90 min. Endothelium-dependent dilation was assessed via brachial artery flow-mediated dilation (FMD) and expressed as % increase in diameter from baseline before forearm occlusion. Results: Lipid infusion significantly increase plasma fatty acid concentrations (w/o AA: +36 ± 18 vs. with AA: +41 ± 13 vs. μmol/L, P=0.84). AA infusion significantly increased plasma ascorbic acid concentrations (w/o AA: -1 ± 7 vs. with AA: +26 ± 11 μmol/L, P=0.04). Compared with baseline, FMD was significantly reduced following lipid infusion at (Baseline: 9.3 ± 1.1 vs. 20 min: 4.4 ± 1.3 vs. End: 5.3 ± 2.9 %, P=0.03), and when statistically adjusting for the stimulus (shear rate area under the curve) via analysis of covariance (P=0.02). FMD was also significantly reduced following lipid infusion with co-infusion of AA (Baseline: 8.9 ± 1.0 vs. 20 min: 5.3 ± 1.0 vs. End: 6.4 ± 3.8 %, P=0.02), but not when statistically adjusting for shear rate under the curve (P=0.08). Conclusions: Elevated plasma fatty acids impair endothelium-dependent dilation in healthy adults. However, co-administration of an antioxidant (ascorbic acid) limited the reduction in FMD when correcting for shear rate. Therefore, these preliminary data suggest that fatty acids may reduce endothelium-dependent dilation via an oxidative stress mechanism. Funding and support: R01HL159370-01 (S.W.H.). This work was also supported by a CTSA grant from NCATS awarded to the University of Kansas for Frontiers: University of Kansas Clinical and Translational Science Institute (# UL1TR002366). The contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIH or CTSA. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Microvascular constriction via fatty acid-mediated oxidative stress in humans

Purpose: Excess plasma lipids promote oxidative stress and impair vascular function. Herein, we examined microcirculatory blood flow and tested the hypothesis that a co-infusion of a water-soluble antioxidant (ascorbic acid, AA) would attenuate reductions in retinal arteriole lumen diameter and increase resistance resulting from acutely elevated plasma lipids in healthy adults. Methods: A 20% IV fat emulsion (Intralipid) was administered for 2 hours to 8 healthy, middle-aged adults (2 men/6 women) with and without co-infusion of ascorbic acid (separate visits) in a double-blinded, crossover study design. Co-infusion of AA was administered at 0.06g/kg fat free mass in 100 ml saline at 5 mL/min over 20 min (bolus) followed by a drip infusion at 0.02 g/kg fat-free mass in 30 ml saline at 0.33 mL/min over 90 min. Retinal arteriole lumen diameter and resistance were assessed via Laser Speckle Flowgraphy at baseline and after infusion. Results: Lipid infusion significantly increase plasma fatty acid concentrations (lipid w/o AA: +36 ± 18 vs. lipid with AA: +41 ± 13 vs. μmol/L, P=0.84). AA infusion significantly increased plasma ascorbic acid concentrations (lipid w/o AA: -1 ± 7 vs. lipid with AA: +26 ± 11 μmol/L, P=0.04). A significant increase in retinal arteriole resistance was observed following lipid infusion (lipid w/o AA: +20 ± 8 %, vs. lipid with AA: +17 ± 8 %, P=0.40). In accordance, lipid infusion significantly reduced retinal arteriole lumen diameter; however, co-infusion of AA reversed the lipid-mediated decrease in retinal arteriole diameter (lipid w/o AA: -3 ± 1 % vs. lipid with AA: +3 ± 2 %, P=0.01). Conclusions: Although microvascular resistance was increased, co-infusion of the antioxidant (ascorbic acid) reversed the fatty acid-mediated reduction in arteriole lumen diameter. Therefore, these preliminary findings suggest that acute elevations in plasma fatty acids induce microvascular constriction via an oxidative stress pathway. Funding and support: R01HL159370-01 (S.W.H.). This work was also supported by a CTSA grant from NCATS awarded to the University of Kansas for Frontiers: University of Kansas Clinical and Translational Science Institute (# UL1TR002366). The contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIH or CTSA. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.