Microvascular insulin resistance associates with enhanced muscle glucose disposal in CD36 deficiency.

Dysfunction of endothelial insulin delivery to muscle associates with insulin resistance. CD36, a fatty acid transporter and modulator of insulin signaling is abundant in endothelial cells, especially in capillaries. Humans with inherited 50% reduction in CD36 expression have endothelial dysfunction but whether it is associated with insulin resistance is unclear. Using hyperinsulinemic/euglycemic clamps in Cd36-/- and wildtype mice, and in 50% CD36 deficient humans and matched controls we found that Cd36-/- mice have enhanced systemic glucose disposal despite unaltered transendothelial insulin transfer and reductions in microvascular perfusion and blood vessel compliance. Partially CD36 deficient humans also have better glucose disposal than controls with no capillary recruitment by insulin. CD36 knockdown in primary human-derived microvascular cells impairs insulin action on AKT, endothelial nitric oxide synthase, and nitric oxide release. Thus, insulin resistance of microvascular function in CD36 deficiency paradoxically associates with increased glucose utilization, likely through a remodeling of muscle gene expression.

A randomized controlled pilot trial of anakinra and pioglitazone for protein metabolism in patients on maintenance haemodialysis.

BACKGROUND: Chronic inflammation and insulin resistance are highly prevalent in patients on maintenance haemodialysis (MHD) and are strongly associated with protein energy wasting. We conducted a pilot, randomized, placebo-controlled trial of recombinant human interleukin-1 receptor antagonist (IL-1ra) and pioglitazone to explore the safety, feasibility and efficacy for insulin-mediated protein metabolism in patients undergoing MHD. METHODS: Twenty-four patients were randomized to receive IL-1ra, pioglitazone or placebo for 12 weeks. Changes in serum inflammatory markers and insulin-mediated protein synthesis, breakdown and net balance in the whole-body and skeletal muscle compartments were assessed using hyperinsulinaemic-hyperaminoacidemic clamp technique at baseline and Week 12. RESULTS: Among 24 patients, median (interquartile range) age was 51 (40, 61), 79% were African American and 21% had diabetes mellitus. All patients initiated on intervention completed the study, and no serious adverse events were observed. There was a statistically significant decrease in serum high-sensitivity C-reactive protein in the pioglitazone group compared with placebo, but not in the IL-1ra group. No significant differences in the changes of whole-body or skeletal muscle protein synthesis, breakdown and net balance were found between the groups. CONCLUSIONS: In this pilot study, there were no statistically significant effects of 12 weeks of IL-1ra or pioglitazone on protein metabolism in patients on MHD. CLINICALTRIALS: gov registration: NCT02278562.

Intraduodenal nutrient infusion differentially alters intestinal nutrient sensing, appetite, and satiety responses in lean and obese subjects.

BACKGROUND: Intestinal nutrient sensing regulates food intake and energy metabolism by acting locally and relaying nutritional status to the brain. It is unclear whether these mechanisms are altered in obese humans. OBJECTIVES: We aimed to investigate differences in duodenal nutrient sensing in humans with or without obesity and the effects of transiently blocking vagal transmission on nutrient sensing, hunger, and appetite. METHODS: In a single-blinded, randomized, cross-over design, subjects with or without obesity (n = 14 and n = 11, respectively) were infused intraduodenally with saline or a combination of glucose and oleic acid for 90 min (glucose load: 22.5 g, 1 kcal/min; oleic acid load: 10 g, 1 kcal/min) in the presence or absence of local anesthetic (benzocaine). Blood was sampled at 10-min intervals (120-240 min) and 15-min intervals until termination of the study for measurements of gut hormones, insulin, leptin, and C-peptide. Hunger and satiety sensations were scored using the visual analog scale, and hepatic glucose production and glucose oxidation rates were measured. RESULTS: Duodenal nutrient infusion in lean subjects led to a 65% drop in acyl ghrelin release and robustly increased cholecystokinin 8 (CCK-8) release (65%; P = 0.023); benzocaine infusion delayed this response (2-factor repeated-measures analysis of variance, P = 0.0065). In contrast, subjects with obesity had significantly blunted response to nutrient infusion, and no further effects were observed with benzocaine. Additionally, significant delays were observed in peptide YY (3-36), pancreatic polypeptide, glucose inhibitory peptide, and glucagon-like peptide 1 (7-36) response. No significant interactions were found between body mass index (BMI) or baseline hormone levels and areas under the curve for hormones except CCK-8 (BMI, P = 0.018; baseline CCK, P = 0.013). Nutrient-induced hunger and satiety sensations were impeded by benzocaine only in the lean cohort. Hunger and satiety sensations in subjects with obesity were not responsive to nutrient entry into the duodenum, and no additional effects were observed by blocking neural signaling. CONCLUSION: Nutrient-induced gut hormone release and response to transient vagal blockade are significantly blunted in subjects with obesity. This trial was registered at clinicaltrials.org as NCT02537314.

Inflammation Biomarker Response to Oral 2-Hydroxybenzylamine (2-HOBA) Acetate in Healthy Humans.

Inflammation is associated with the formation of reactive oxygen species (ROS) and the formation of lipid-derived compounds, such as isolevuglandins (IsoLGs), malondialdehyde, 4-hydroxy-nonenal, and 4-oxo-nonenal. The most reactive of these are the IsoLGs, which form covalent adducts with lysine residues and other cellular primary amines leading to changes in protein function, immunogenicity, and epigenetic alterations and have been shown to contribute to a number of inflammatory diseases. 2-Hydroxybenzylamine (2-HOBA) is a natural compound found in buckwheat seeds and reacts with all IsoLG adducts preventing adduct formation with proteins and DNA. Therefore, 2-HOBA is well positioned as an agent for the prevention of inflammatory-prone diseases. In this study, we examined the potential beneficial effects of 2-HOBA on oxidative stress and inflammatory biomarkers in two cohorts of healthy younger and older adults. We utilized the Olink® targeted inflammation panel before and after an oral 15-day treatment regimen with 2-HOBA. We found significant relative changes in the plasma concentration of 15 immune proteins that may reflect the in vivo immune targets of 2-HOBA. Treatment of 2-HOBA resulted in significant increased levels of CCL19, IL-12ß, IL-20Rα, and TNFß, whereas levels of TWEAK significantly decreased. Ingenuity Pathway Analysis identified canonical pathways regulated by the differentially secreted cytokines, chemokines, and growth factors upon 2-HOBA treatment and further points to biofunctions related to the recruitment, attraction, and movement of different immune cell types. In conclusion, 2-HOBA significantly altered the protein biomarkers CCL19, IL-12ß, IL-20Rα, TNFß, and TWEAK, and these may be responsible for the protective effects of 2-HOBA against reactive electrophiles, such as IsoLGs, commonly expressed in conditions of excessive oxidative stress. 2-HOBA has a role as a IsoLG scavenger to proactively improve immune health in a variety of conditions.

Caloric Restriction and Weight Loss Are Primary Factors in the Early Tissue-Specific Metabolic Changes After Bariatric Surgery.

OBJECTIVE: To evaluate changes in insulin sensitivity, hormone secretion, and hepatic steatosis immediately after caloric restriction, vertical sleeve gastrectomy (VSG), and Roux-en-Y gastric bypass (RYGB). RESEARCH DESIGN AND METHODS: Obese subjects were assessed for 1) insulin sensitivity with hyperinsulinemic-euglycemic clamp with glucose tracer infusion, 2) adipokine concentrations with serum and subcutaneous adipose interstitial fluid sampling, and 3) hepatic fat content with MRI before and 7-10 days after VSG, RYGB, or supervised caloric restriction. RESULTS: Each group exhibited an ∼5% total body weight loss, accompanied by similar improvements in hepatic glucose production and hepatic, skeletal muscle, and adipose tissue insulin sensitivity. Leptin concentrations in plasma and adipose interstitial fluid were equally decreased, and reductions in hepatic fat were similar. CONCLUSIONS: The improvements in insulin sensitivity and adipokine secretion observed early after bariatric surgery are replicated by equivalent caloric restriction and weight loss.

Intestinal Lymph Collection via Cannulation of the Mesenteric Lymphatic Duct in Mice.

BACKGROUND: We have optimized a technique for cannulation of mesenteric lymph duct (MLD) in mice. Mice have low rates of intestinal lymph production; the MLDs are smaller and associated with fragile vasculature. Previous protocols for lymph collection based on the open lymph fistula model were associated with low success rates in mice. Bariatric surgery procedures worsen success rates due to postoperative adhesions and GI rearrangement. We have used this procedure to collect mesenteric lymph from mice undergoing bile diversion from gall bladder to ileum (GB-IL). HYPOTHESIS: We hypothesize that peptide YY (PYY) levels in mesenteric lymph will increase following nutrient delivery in mice undergoing bile diversion from gall bladder to ileum (GB-IL). METHODS AND RESULTS: We observe that cannulation of the MLD using a needled-catheter maintains lymph vessel integrity, prevents excessive lymph leakage, and is less traumatic, leading to high success rates (>95%). PYY levels in mesenteric lymph after GB-IL were significantly higher post nutrient infusion. The procedure takes approximately 20 min; small rodent surgical experience and practice are required for success. CONCLUSIONS: Intestinal lymph can be collected from mice, including those undergoing bariatric surgical procedures with high success rates by cannulation of the mesenteric lymph duct.

Safety, tolerability, and pharmacokinetics of repeated oral doses of 2-hydroxybenzylamine acetate in healthy volunteers: a double-blind, randomized, placebo-controlled clinical trial.

BACKGROUND: 2-Hydroxybenzylamine (2-HOBA) is a selective dicarbonyl electrophile scavenger being developed as a nutritional supplement to help protect against the development of conditions associated with dicarbonyl electrophile formation, such as the cognitive decline observed with Mild Cognitive Impairment or Alzheimer's disease. METHODS: This study evaluated the safety, tolerability, and pharmacokinetics of repeated oral doses of 2-HOBA acetate (500 or 750 mg) administered to healthy volunteers every eight hours for two weeks. The effects of 2-HOBA on cyclooxygenase function and cerebrospinal fluid penetrance of 2-HOBA were also investigated. RESULTS: Repeated oral administration of 2-HOBA was found to be safe and well-tolerated up to 750 mg TID for 15 days. 2-HOBA was absorbed within 2 h of administration, had a half-life of 2.10-3.27 h, and an accumulation ratio of 1.38-1.52. 2-HOBA did not interfere with cyclooxygenase function and was found to be present in cerebrospinal fluid 90 min after dosing. CONCLUSIONS: Repeated oral administration of 2-HOBA was found to be safe and well-tolerated. These results support continued development of 2-HOBA as a nutritional supplement. TRIAL REGISTRATION: Studies are registered at ClinicalTrials.gov (NCT03555682 Registered 13 June 2018, NCT03554096 Registered 12 June 18).

Iatrogenic Hyperinsulinemia, Not Hyperglycemia, Drives Insulin Resistance in Type 1 Diabetes as Revealed by Comparison With GCK-MODY (MODY2).

Although insulin resistance consistently occurs with type 1 diabetes, its predominant driver is uncertain. We therefore determined the relative contributions of hyperglycemia and iatrogenic hyperinsulinemia to insulin resistance using hyperinsulinemic-euglycemic clamps in three participant groups (n = 10/group) with differing insulinemia and glycemia: healthy control subjects (euinsulinemia and euglycemia), glucokinase-maturity-onset diabetes of the young (GCK-MODY; euinsulinemia and hyperglycemia), and type 1 diabetes (hyperinsulinemia and hyperglycemia matching GCK-MODY). We assessed the contribution of hyperglycemia by comparing insulin sensitivity in control and GCK-MODY and the contribution of hyperinsulinemia by comparing GCK-MODY and type 1 diabetes. Hemoglobin A1c was normal in control subjects and similarly elevated for type 1 diabetes and GCK-MODY. Basal insulin levels in control subjects and GCK-MODY were nearly equal but were 2.5-fold higher in type 1 diabetes. Low-dose insulin infusion suppressed endogenous glucose production similarly in all groups and suppressed nonesterified fatty acids similarly between control subjects and GCK-MODY, but to a lesser extent for type 1 diabetes. High-dose insulin infusion stimulated glucose disposal similarly in control subjects and GCK-MODY but was 29% and 22% less effective in type 1 diabetes, respectively. Multivariable linear regression showed that insulinemia-but not glycemia-was significantly associated with muscle insulin sensitivity. These data suggest that iatrogenic hyperinsulinemia predominates in driving insulin resistance in type 1 diabetes.

Metabolic Effects of Bile Acids: Potential Role in Bariatric Surgery.

Bariatric surgery is the most effective and durable treatment for morbid obesity, with an unexplained yet beneficial side effect of restoring insulin sensitivity and improving glycemia, often before weight loss is observed. Among the many contributing mechanisms often cited, the altered handling of intestinal bile acids is of considerable therapeutic interest. Here, we review a growing body of literature examining the metabolic effects of bile acids ranging from their physical roles in dietary fat handling within the intestine to their functions as endocrine and paracrine hormones in potentiating responses to bariatric surgery. The roles of 2 important bile acid receptors, Takeda G-protein coupled receptor (also known as G-protein coupled bile acid receptor) and farnesoid X receptor, are highlighted as is downstream signaling through glucagon-like polypeptide 1 and its cognate receptor. Additional improvements in other phenotypes and potential contributions of commensal gut bacteria, such as Akkermansia muciniphila, which are manifest after Roux-en-Y gastric bypass and other emulations, such as gallbladder bile diversion to the ileum, are also discussed.

Brief communication: ß-cell function influences dopamine receptor availability.

We aim to identify physiologic regulators of dopamine (DA) signaling in obesity but previously did not find a compelling relationship with insulin sensitivity measured by oral-minimal model (OMM) and DA subtype 2 and 3 receptor (D2/3R) binding potential (BPND). Reduced disposition index (DI), a ß-cell function metric that can also be calculated by OMM, was shown to predict a negative reward behavior that occurs in states of lower endogenous DA. We hypothesized that reduced DI would occur with higher D2/3R BPND, reflecting lower endogenous DA. Participants completed PET scanning, with a displaceable radioligand to measure D2/3R BPND, and a 5-hour oral glucose tolerance test to measure DI by OMM. We studied 26 age-similar females without (n = 8) and with obesity (n = 18) (22 vs 39 kg/m2). Reduced DI predicted increased striatal D2/3R BPND independent of BMI. By accounting for ß-cell function, we were able to determine that the state of insulin and glucose metabolism is pertinent to striatal D2/3R BPND in obesity. Clinical Trial Registration Number: NCT00802204.

New-Onset Post-Transplant Diabetes Mellitus after Allogeneic Hematopoietic Cell Transplant Is Initiated by Insulin Resistance, Not Immunosuppressive Medications.

New-onset post-transplant diabetes mellitus (PTDM) occurs frequently after allogeneic hematopoietic cell transplant (HCT). Although calcineurin inhibitors and corticosteroids are assumed to be the cause for hyperglycemia, patients developing PTDM have elevated fasting C-peptide levels before HCT and before immunosuppressive medications. To determine if PTDM results from established insulin resistance present before transplant, we performed oral glucose tolerance tests (OGTTs) and measured whole body, peripheral, and hepatic insulin sensitivity with euglycemic hyperinsulinemic clamps before and 90 days after HLA-identical sibling donor HCT in 20 patients without pretransplant diabetes. HCT recipients were prospectively followed for the development of new-onset PTDM defined as a weekly fasting blood glucose ≥ 126 mg/dL or random blood glucose ≥ 200 mg/dL. During the first 100 days all patients received calcineurin inhibitors, and 11 individuals (55%) were prospectively diagnosed with new-onset PTDM. PTDM diagnosis preceded corticosteroid treatment. During the pretransplant OGTT, elevated fasting (87 mg/dL versus 101 mg/dL; P = .005) but not 2-hour postprandial glucose levels predicted PTDM diagnosis (P = .648). In response to insulin infusion during the euglycemic hyperinsulinemic clamp, patients developing PTDM had lower whole body glucose utilization (P = .047) and decreased peripheral/skeletal muscle uptake (P = .031) before and after transplant, respectively, when compared with non-PTDM patients. Hepatic insulin sensitivity did not differ. Survival was decreased in PTDM patients (2-year estimate, 55% versus 100%; P = .039). Insulin resistance before HCT is a risk factor for PTDM independent of immunosuppression. Fasting pretransplant glucose levels identified PTDM susceptibility, and peripheral insulin resistance could be targeted for prevention and treatment of PTDM after HCT.

First-in-human study assessing safety, tolerability, and pharmacokinetics of 2-hydroxybenzylamine acetate, a selective dicarbonyl electrophile scavenger, in healthy volunteers.

BACKGROUND: 2-Hydroxybenzylamine (2-HOBA) is a selective scavenger of dicarbonyl electrophiles that protects proteins and lipids from being modified by these electrophiles. It is currently being developed for use as a nutritional supplement to help maintain good health and protect against the development of conditions associated with dicarbonyl electrophile formation, such as the cognitive decline associated with Mild Cognitive Impairment and Alzheimer's disease. METHODS: In this first-in-human study, the safety, tolerability, and pharmacokinetics of six ascending single oral doses of 2-HOBA acetate were tested in eighteen healthy human volunteers. RESULTS: Reported adverse events were mild and considered unlikely to be related to 2-HOBA. There were no clinically significant changes in vital signs, ECG recordings, or clinical laboratory parameters. 2-HOBA was fairly rapidly absorbed, with a tmax of 1-2 h, and eliminated, with a t1/2 of approximately 2 h. Both tmax and t1/2 were independent of dose level, while Cmax and AUC increased proportionally with dose level. CONCLUSIONS: 2-HOBA acetate was safe and well-tolerated at doses up to 825 mg in healthy human volunteers, positioning it as a good candidate for continued development as a nutritional supplement. TRIAL REGISTRATION: This study is registered at ClinicalTrials.gov (NCT03176940).

Role of Bile Acids and GLP-1 in Mediating the Metabolic Improvements of Bariatric Surgery.

BACKGROUND & AIMS: Bile diversion to the ileum (GB-IL) has strikingly similar metabolic and satiating effects to Roux-en-Y gastric bypass (RYGB) in rodent obesity models. The metabolic benefits of these procedures are thought to be mediated by increased bile acids, although parallel changes in body weight and other confounding variables limit this interpretation. METHODS: Global G protein-coupled bile acid receptor-1 null (Tgr5-/-) and intestinal-specific farnesoid X receptor null (FxrΔ/E) mice on high-fat diet as well as wild-type C57BL/6 and glucagon-like polypeptide 1 receptor deficient (Glp-1r-/-) mice on chow diet were characterized following GB-IL. RESULTS: GB-IL induced weight loss and improved oral glucose tolerance in Tgr5-/-, but not FxrΔ/E mice fed a high-fat diet, suggesting a role for intestinal Fxr. GB-IL in wild-type, chow-fed mice prompted weight-independent improvements in glycemia and glucose tolerance secondary to augmented insulin responsiveness. Improvements were concomitant with increased levels of lymphatic GLP-1 in the fasted state and increased levels of intestinal Akkermansia muciniphila. Improvements in fasting glycemia after GB-IL were mitigated with exendin-9, a GLP-1 receptor antagonist, or cholestyramine, a bile acid sequestrant. The glucoregulatory effects of GB-IL were lost in whole-body Glp-1r-/- mice. CONCLUSIONS: Bile diversion to the ileum improves glucose homeostasis via an intestinal Fxr-Glp-1 axis. Altered intestinal bile acid availability, independent of weight loss, and intestinal Akkermansia muciniphila appear to mediate the metabolic changes observed after bariatric surgery and might be manipulated for treatment of obesity and diabetes.

Subchronic (90-day) repeated dose oral toxicity study of 2-hydroxybenzylamine acetate in rabbit.

2-hydroxybenzylamine (2-HOBA), a naturally occurring compound found in buckwheat, has potential for use as a nutrition supplement due to its ability to protect against the damaging effects of oxidative stress. In a series of rodent toxicity studies, 2-HOBA acetate was well-tolerated and did not produce any toxic effects over 28 or 90 days of repeated oral administration. However, it remained necessary to test the potential toxicity of 2-HOBA acetate in a non-rodent species. In this investigation, 2-HOBA acetate was orally administered to male and female New Zealand White Rabbits for 90 days at doses of 100, 500, and 1000 mg·kg BW-1·day-1 (n = 5 per sex/group). As previously observed in rodents, 2-HOBA acetate administration was well tolerated. No toxic effects of 2-HOBA acetate were detected in body weight, feed consumption, hematology, blood chemistry, urine chemistry, organ weights, gross pathology or histopathology. Based on these findings, the no-observed-adverse-effect-level of 2-HOBA acetate in rabbits was determined to be 1000 mg·kg BW-1·day-1, which was the highest dose tested. These results provide further support for the safety of 2-HOBA acetate administration.

Attenuation of diet-induced hypothalamic inflammation following bariatric surgery in female mice.

BACKGROUND: Exposure of rodents to chronic high-fat diet (HFD) results in upregulation of inflammatory markers and proliferation of microglia within the mediobasal hypothalamus. Such hypothalamic inflammation is associated with metabolic dysfunction, central leptin resistance, and maintenance of obesity. Bariatric surgeries result in long-term stable weight loss and improved metabolic function. However, the effects of such surgical procedures on HFD-induced hypothalamic inflammation are unknown. We sought to characterize the effects of two bariatric surgical procedures, Roux-en-Y gastric bypass (RYGB) and biliary diversion (BD-IL), in female mice with particular emphasis on HFD-induced hypothalamic inflammation and microgliosis. METHODS: RYGB and BD-IL were performed on diet-induced obese (DIO) mice. Quantitative RT-PCR and fluorescent microscopy were used to evaluate hypothalamic inflammatory gene expression and microgliosis. Results were compared to lean (CD), DIO sham-surgerized mice (DIO-SHAM), and dietary weight loss (DIO-Rev) controls. RESULTS: In female mice, RYGB and BD-IL result in normalization of hypothalamic inflammatory gene expression and microgliosis within 8 weeks of surgery, despite ongoing exposure to HFD. Paralleling these results, the hypothalamic expression levels of the orexigenic neuropeptide Agrp and the anorexic response of surgical mice to exogenous leptin were comparable to lean controls (CD). In contrast, results from DIO-Rev mice were comparable to DIO-SHAM mice, despite transition back to standard rodent show and normalization of weight. CONCLUSION: Bariatric surgery attenuates HFD-induced hypothalamic inflammation and microgliosis and restores leptin sensitivity, despite ongoing exposure to HFD.

In vitro safety pharmacology evaluation of 2-hydroxybenzylamine acetate.

2-hydroxybenzylamine (2-HOBA), a compound found in buckwheat, is a potent scavenger of reactive γ-ketoaldehydes, which are increased in diseases associated with inflammation and oxidative stress. While the potential of 2-HOBA is promising, studies were needed to characterize the safety of the compound before clinical trials. In a series of experiments, the risks of 2-HOBA-mediated mutagenicity and cardio-toxicity were assessed in vitro. The effects of 2-HOBA on the mRNA expression of select cytochrome P450 (CYP) enzymes were also assessed in cryopreserved human hepatocytes. Further, the distribution and metabolism of 2-HOBA in blood were determined. Our results indicate that 2-HOBA is not cytotoxic or mutagenic in vitro and does not induce the expression of CYP1A2, CYP2B6, or CYP3A4 in human hepatocytes. The results of the hERG testing showed a low risk of cardiac QT wave prolongation. Plasma protein binding and red blood cell distribution characteristics indicate low protein binding and no preferential distribution into erythrocytes. The major metabolites identified were salicylic acid and the glycoside conjugate of 2-HOBA. Together, these findings support development of 2-HOBA as a nutritional supplement and provide important information for the design of further preclinical safety studies in animals as well as for human clinical trials with 2-HOBA.

Subchronic (90-day) repeated dose toxicity study of 2-hydroxybenzylamine acetate in rats.

2-Hydroxybenzylamine (2-HOBA), a naturally occurring compound found in buckwheat, can protect cells and tissues from oxidative stress. In this study, 2-HOBA acetate was orally administered to male and female rats for 90 consecutive days at doses of 100, 500, and 1000 mg·kg BW-1·d-1 (n = 20 per sex/group). Subchronic administration of 2-HOBA was well tolerated at all dose levels. 2-HOBA-treated male rats were slightly heavier in the last weeks of the study, but this difference was very small (<5%), did not show a dose-response relationship, and was not observed in female rats. Similarly, some statistically significant changes in serum biochemistry and hematology parameters were noted, but these were not considered to be of biological or toxicological significance. Sporadic differences in organ weights were observed between groups, but all were small (<10%) and unlikely to indicate toxicity. The incidence of histopathological lesions was similar between treated and control groups across all organs. Based upon these findings, the no-observed-adverse-effect level was determined to be ≥ 1000 mg·kg BW-1·d-1, which was the highest dose tested. These results further support no toxicity associated with oral consumption of 2-HOBA acetate in rats and the continued development of 2-HOBA as a dietary supplement or functional food.

Acute and 28-day repeated dose toxicity evaluations of 2-hydroxybenzylamine acetate in mice and rats.

2-hydroxybenzylamine (2-HOBA), a compound naturally found in buckwheat, has been shown to protect cells and tissues from the damaging effects of oxidative stress. The purpose of this report was to evaluate 2-HOBA in preclinical oral rodent toxicity studies. This report includes the results from three oral toxicity studies in rodents: a preliminary 28-day feeding study in mice, a 14-day acute oral toxicity study in rats, and a 28-day repeated dose oral toxicity study in rats. The preliminary mouse feeding study showed no adverse effects of 2-HOBA at concentrations up to 0.456% by weight in feed, but decreased food intake and weight loss were observed at 1.56% 2-HOBA in the diet, likely due to poor palatability. In the acute dosing study, 2000 mg/kg BW 2-HOBA resulted in mortality in one of the six tested female rats, indicating a median lethal dose of 2500 mg/kg BW. In the 28-day repeated oral dose study, small differences were observed between 2-HOBA treated and control group rats, but none of these differences were determined to be of toxicological significance. Together, these studies support the lack of toxicity of oral administration of 2-HOBA acetate at doses up to 1000 mg/kg BW d-1 in rodents.

Bile diversion, a bariatric surgery, and bile acid signaling reduce central cocaine reward.

The gut-to-brain axis exhibits significant control over motivated behavior. However, mechanisms supporting this communication are poorly understood. We reveal that a gut-based bariatric surgery chronically elevates systemic bile acids and attenuates cocaine-induced elevations in accumbal dopamine. Notably, this surgery reduces reward-related behavior and psychomotor sensitization to cocaine. Utilizing a knockout mouse model, we have determined that a main mediator of these post-operative effects is the Takeda G protein-coupled bile acid receptor (TGR5). Viral restoration of TGR5 in the nucleus accumbens of TGR5 knockout animals is sufficient to restore cocaine reward, centrally localizing this TGR5-mediated modulation. These findings define TGR5 and bile acid signaling as pharmacological targets for the treatment of cocaine abuse and reveal a novel mechanism of gut-to-brain communication.

Insulin resistance is a significant determinant of sarcopenia in advanced kidney disease.

Maintenance hemodialysis (MHD) patients display significant nutritional abnormalities. Insulin is an anabolic hormone with direct effects on skeletal muscle (SM). We examined the anabolic actions of insulin, whole-body (WB), and SM protein turnover in 33 MHD patients and 17 participants without kidney disease using hyperinsulinemic-euglycemic-euaminoacidemic (dual) clamp. Gluteal muscle biopsies were obtained before and after the dual clamp. At baseline, WB protein synthesis and breakdown rates were similar in MHD patients. During dual clamp, controls had a higher increase in WB protein synthesis and a higher suppression of WB protein breakdown compared with MHD patients, resulting in statistically significantly more positive WB protein net balance [2.02 (interquartile range [IQR]: 1.79 and 2.36) vs. 1.68 (IQR: 1.46 and 1.91) mg·kg fat-free mass-1·min-1 for controls vs. for MHD patients, respectively, P < 0.001]. At baseline, SM protein synthesis and breakdown rates were higher in MHD patients versus controls, but SM net protein balance was similar between groups. During dual clamp, SM protein synthesis increased statistically significantly more in controls compared with MHD patients ( P = 0.03), whereas SM protein breakdown decreased comparably between groups. SM net protein balance was statistically significantly more positive in controls compared with MHD patients [67.3 (IQR: 46.4 and 97.1) vs. 15.4 (IQR: -83.7 and 64.7) µg·100 ml-1·min-1 for controls and MHD patients, respectively, P = 0.03]. Human SM biopsy showed a positive correlation between glucose and leucine disposal rates, phosphorylated AKT to AKT ratio, and muscle mitochondrial markers in controls but not in MHD patients. Diminished response to anabolic actions of insulin in the stimulated setting could lead to muscle wasting in MHD patients.