Reduced Plasma Insulin Research Articles

7279 Survodutide and Semaglutide Both Induce Weight Loss but Show Different Effects on Food Preference and Dyslipidemia in the Free Choice Diet-induced Obese Hamster Model

Abstract Disclosure: F. Briand: Employee; Self; Physiogenix. R. Augustin: Employee; Self; Boehringer Ingelheim. K. Bleymehl: Employee; Self; Boehringer Ingelheim. T. Zimmermann: Employee; Self; Boehringer Ingelheim. T. Klöckener: Employee; Self; Boehringer Ingelheim. T. Klein: Employee; Self; Boehringer Ingelheim. Introduction: Semaglutide, a GLP-1 receptor agonist, and survodutide, a GCGR/GLP-1R dual agonist, have demonstrated significant weight loss in patients with obesity. To test whether this weight loss is associated with changes in food preference and improvement in dyslipidemia, we evaluated semaglutide and survodutide in the free choice diet-induced obese and dyslipidemic hamster, a model with a human-like lipoprotein metabolism. Methods: Obesity and dyslipidemia were induced with a 20-week free choice diet, which presents hamsters with a choice between control chow diet or high fat/cholesterol diet, and normal water or 10% fructose water. Obese hamsters were then kept on this free choice diet and treated subcutaneously once daily with vehicle, semaglutide 15 nmol/kg or survodutide 15 nmol/kg for 5 weeks. Results: Compared with vehicle, semaglutide and survodutide led to a 17% and 11% body weight reduction, respectively (both p<0.001 vs vehicle). Compared to vehicle, both chow diet and high fat diet intakes were significantly lower during the first week of semaglutide treatment, but then returned to baseline values. However, semaglutide significantly increased normal water intake and reduced fructose-enriched water intake during the whole treatment period (both p<0.001). Survodutide had a different effect, as it did not alter chow diet and normal water intakes, but significantly reduced high fat diet and fructose-enriched water intakes during the 5-week treatment period. Semaglutide and survodutide significantly reduced plasma insulin levels and the HOMA-IR index of insulin resistance (both p<0.01 vs. vehicle). Both semaglutide and survodutide significantly reduced plasma total cholesterol levels by 24% and 41%, respectively (both p<0.001). This hypocholesterolemic effect led to lower HDL-cholesterol levels (-25%, p<0.001) but unchanged LDL-cholesterol levels for hamsters treated with semaglutide. In contrast, in hamsters treated with survodutide, cholesterol lowering was observed in all lipoprotein fractions, including LDL-cholesterol (-39%, p<0.001). Conclusion: Semaglutide and survodutide both induce weight loss and lower HOMA-IR, but have different effects on food preference and dyslipidemia in the obese hamster model; such effects may be attributed to the GCGR agonism of survodutide. These preclinical data highlight the potential metabolic benefits of the GCGR/GLP-1R dual agonist survodutide for the treatment of obesity and related metabolic comorbidities. Presentation: 6/3/2024

Amylase and lipase levels in the metabolic syndrome and type 2 diabetes: A longitudinal study in rhesus monkeys.

Latent associations between low serum amylase and reduced plasma insulin levels and increased adiposity have been described previously in a small study of asymptomatic middle-aged humans. In the present study, we sought to determine the nature of such changes during the longitudinal progression from metabolically normal to overt type 2 diabetes mellitus (T2DM) in nonhuman primates (NHPs), a disease that appears to be the same in both pathophysiology and underlying mechanisms as that which most commonly develops in middle-aged adult humans. Amylase and lipase levels were characterized in 157 unrelated adult rhesus monkeys (Macaca mulatta); 38% developed T2DM while under study. In all monkeys, multivariable linear regression analysis revealed that amylase could be negatively predicted by % body fat (β -0.29; p = 0.002), age (β -0.27; p = 0.005), and HbA1c (β -0.18; p = 0.037). Amylase levels were positively predicted by lipase levels (β = 0.19; p = -0.024) in all NHPs included in the study. Amylase was significantly lower in NHPs with metabolic syndrome (p < 0.001), prediabetes (PreDM) (p < 0.001), and T2DM (p < 0.001) compared to metabolically normal adult NHPs. Lipase increased in NHPs with PreDM (p = 0.005) and T2DM (p = 0.04) compared to normal NHPs. This is the first longitudinal study of any species, including humans, to show the dynamics of amylase and lipase during the metabolic progression from normal to metabolic syndrome, to PreDM and then to overt T2DM. The extraordinary similarity between humans and monkeys in T2DM, in pancreatic pathophysiology and in metabolic functions give these findings high translational value.

Plasma Insulin Predicts Early Amyloid-β Pathology Changes in Alzheimer's Disease.

Evidence suggests that type 2 diabetes (T2D) is an independent risk factor for Alzheimer's disease (AD), sharing similar pathophysiological traits like impaired insulin signaling. To test the association between plasma insulin and cerebrospinal fluid (CSF) AD pathology. A total of 304 participants were included in the Alzheimer's Disease Neuroimaging Initiative, assessing plasma insulin and CSF AD pathology. We explored the cross-sectional and longitudinal associations between plasma insulin and AD pathology and compared their associations across different AD clinical and pathological stages. In the non-demented group, amyloid-β (Aβ)+ participants (e.g., as reflected by CSF Aβ42) exhibited significantly lower plasma insulin levels compared to non-demented Aβ-participants (p < 0.001). This reduction in plasma insulin was more evident in the A+T+ group (as shown by CSF Aβ42 and pTau181 levels) when compared to the A-T- group within the non-dementia group (p = 0.002). Additionally, higher plasma insulin levels were consistently associated with more normal CSF Aβ42 levels (p < 0.001) across all participants. This association was particularly significant in the Aβ-group (p = 0.002) and among non-demented individuals (p < 0.001). Notably, baseline plasma insulin was significantly correlated with longitudinal changes in CSF Aβ42 (p = 0.006), whereas baseline CSF Aβ42 did not show a similar correlation with changes in plasma insulin over time. These findings suggest an association between plasma insulin and early Aβ pathology in the early stages of AD, indicating that plasma insulin may be a potential predictor of changes in early Aβ pathology.

Reduced Insulin Resistance and Oxidative Stress in a Mouse Model of Metabolic Syndrome following Twelve Weeks of Citrus Bioflavonoid Hesperidin Supplementation: A Dose-Response Study.

Metabolic syndrome (MetS) is a cluster of metabolic abnormalities affecting ~25% of adults and is linked to chronic diseases such as cardiovascular disease, cancer, and neurodegenerative diseases. Oxidative stress and inflammation are key drivers of MetS. Hesperidin, a citrus bioflavonoid, has demonstrated antioxidant and anti-inflammatory properties; however, its effects on MetS are not fully established. We aimed to determine the optimal dose of hesperidin required to improve oxidative stress, systemic inflammation, and glycemic control in a novel mouse model of MetS. Male 5-week-old C57BL/6 mice were fed a high-fat, high-salt, high-sugar diet (HFSS; 42% kcal fat content in food and drinking water with 0.9% saline and 10% high fructose corn syrup) for 16 weeks. After 6 weeks of HFSS, mice were randomly allocated to either the placebo group or low- (70 mg/kg/day), mid- (140 mg/kg/day), or high-dose (280 mg/kg/day) hesperidin supplementation for 12 weeks. The HFSS diet induced significant metabolic disturbances. HFSS + placebo mice gained almost twice the weight of control mice (p < 0.0001). Fasting blood glucose (FBG) increased by 40% (p < 0.0001), plasma insulin by 100% (p < 0.05), and HOMA-IR by 150% (p < 0.0004), indicating insulin resistance. Hesperidin supplementation reduced plasma insulin by 40% at 140 mg/kg/day (p < 0.0001) and 50% at 280 mg/kg/day (p < 0.005). HOMA-IR decreased by 45% at both doses (p < 0.0001). Plasma hesperidin levels significantly increased in all hesperidin groups (p < 0.0001). Oxidative stress, measured by 8-OHdG, was increased by 40% in HFSS diet mice (p < 0.001) and reduced by 20% with all hesperidin doses (p < 0.005). In conclusion, hesperidin supplementation reduced insulin resistance and oxidative stress in HFSS-fed mice, demonstrating its dose-dependent therapeutic potential in MetS.

AGPAT3 deficiency impairs adipocyte differentiation and leads to a lean phenotype in mice.

Acylglycerophosphate acyltransferases (AGPATs) catalyze the de novo formation of phosphatidic acid to synthesize glycerophospholipids and triglycerides. AGPATs demonstrate unique physiological roles despite a similar biochemical function. AGPAT3 is highly expressed in the testis, kidney, and liver, with intermediate expression in adipose tissue. Loss of AGPAT3 is associated with reproductive abnormalities and visual dysfunction. However, the role of AGPAT3 in adipose tissue and whole body metabolism has not been investigated. We found that male Agpat3 knockout (KO) mice exhibited reduced body weights with decreased white and brown adipose tissue mass. Such changes were less pronounced in the female Agpat3-KO mice. Agpat3-KO mice have reduced plasma insulin growth factor 1 (IGF1) and insulin levels and diminished circulating lipid metabolites. They manifested intact glucose homeostasis and insulin sensitivity despite a lean phenotype. Agpat3-KO mice maintained an energy balance with normal food intake, energy expenditure, and physical activity, except for increased water intake. Their adaptive thermogenesis was also normal despite reduced brown adipose mass and triglyceride content. Mechanistically, Agpat3 was elevated during mouse and human adipogenesis and enriched in adipocytes. Agpat3-knockdown 3T3-L1 cells and Agpat3-deficient mouse embryonic fibroblasts (MEFs) have impaired adipogenesis in vitro. Interestingly, pioglitazone treatment rescued the adipogenic deficiency in Agpat3-deficient cells. We conclude that AGPAT3 regulates adipogenesis and adipose development. It is possible that adipogenic impairment in Agpat3-deficient cells potentially leads to reduced adipose mass. Findings from this work support the unique role of AGPAT3 in adipose tissue.NEW & NOTEWORTHY AGPAT3 deficiency results in male-specific growth retardation. It reduces adipose tissue mass but does not significantly impact glucose homeostasis or energy balance, except for influencing water intake in mice. Like AGPAT2, AGPAT3 is upregulated during adipogenesis, potentially by peroxisome proliferator-activated receptor gamma (PPARγ). Loss of AGPAT3 impairs adipocyte differentiation, which could be rescued by pioglitazone. Overall, AGPAT3 plays a significant role in regulating adipose tissue mass, partially involving its influence on adipocyte differentiation.

AGPAT3 deficiency impairs adipocyte differentiation and leads to a lean phenotype in mice

Acylglycerophosphate acyltransferases (AGPATs) catalyze the de novo formation of phosphatidic acid to synthesize glycerophospholipids and triglycerides. AGPATs demonstrate unique physiological roles despite a similar biochemical function. AGPAT3 is highly expressed in the testis, kidney, and liver, with intermediate expression in adipose tissue. Loss of Agpat3 is associated with reproductive abnormalities and visual dysfunction. However, the role of AGPAT3 in adipose tissue and whole-body metabolism has not been investigated. We found that male Agpat3-KO mice exhibited reduced body weights with decreased white and brown adipose tissue mass. Such changes were less pronounced in the female Agpat3-KO mice. Agpat3-KO mice have reduced plasma insulin growth factor 1 (IGF1) and insulin levels and diminished circulating lipid metabolites. They manifested intact glucose homeostasis and insulin sensitivity despite a lean phenotype. Agpat3-KO mice maintained an energy balance with normal food intake, energy expenditure, and physical activity, except for increased water intake. Their adaptive thermogenesis was also normal despite reduced brown adipose mass and triglyceride content. Mechanistically, Agpat3 was elevated during mouse and human adipogenesis and enriched in adipocytes. Agpat3-knockdown 3T3-L1 cells and Agpat3-deficient mouse embryonic fibroblasts (MEFs) have impaired adipogenesis in vitro. Interestingly, pioglitazone treatment rescued the adipogenic deficiency in Agpat3 deficient cells. We conclude that AGPAT3 regulates adipogenesis and adipose development. It is possible that adipogenic impairment in Agpat3 deficient cells potentially leads to reduced adipose mass. Findings from this work support the unique role of AGPAT3 in adipose tissue. This work was supported by the National Institute of Diabetes and Digestive and Kidney Diseases [1R56 DK135657] and the National Heart, Lung and Blood Institute [2R01HL132182-01] to W.C. 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.

Oligosaccharide feed supplementation reduces plasma insulin in geldings with Equine Metabolic Syndrome

BackgroundThe prevalence of Equine Metabolic Syndrome and insulin dysregulation is increasing in the horse population. Insulin dysregulation is a risk factor for laminitis, which has significant welfare consequences for the horse. Current treatment strategies for Equine Metabolic Syndrome have variable effects on insulin sensitivity. Findings suggest that gut microbiota plays an important role in gastrointestinal barrier protection and metabolic diseases. Dietary supplementation with oligosaccharides has been shown to increase the production of short-chain fatty acids and induce changes in the gut microbiota, with an increase in insulin sensitivity.ObjectivesWe hypothesized that dietary oligosaccharide supplementation would ameliorate insulin dysregulation in horses with Equine Metabolic Syndrome.Study designFifteen horses were included in a cross-over study including two feed supplementations periods with oligosaccharide supplementation or calcium carbonate. Before and after each period plasma insulin, endotoxin, serum amyloid A, and blood glucose concentrations were measured during an oral sugar test and fecal samples were collected.ResultsOligosaccharide supplementation significantly reduced insulin in geldings (p = 0.02). Overall, none of the dominating bacterias changed significantly in relative Δ-abundance. In the gut microbiota of mares, the Akkermansia genus and Clostridiaceae family were significantly more abundant. Within-sample bacterial diversity of horses with insulin concentrations &amp;gt; 60 mIU/L was significantly greater when compared to horses &amp;lt; 60 mIU/L. Horses with insulin concentrations &amp;gt; 60 mIU/L and horses with previous laminitis had a significantly greater beta diversity.Main limitationsCut-off values for oligosaccharide feed supplementation/placebo dosing instead of dosing by g/kg body weight; owner compliance; single blood sample in oral sugar test; inter-horse variationConclusionsThis study demonstrated that oligosaccharide supplementation could improve insulin dysregulation in geldings with Equine Metabolic Syndrome suggesting that sex susceptibility might be a factor to consider. Additionally, a tendency of reduction of obesity-associated bacteria was observed. Furthermore, the diversity of the gut microbiota was significantly dependent on laminitis status and insulin concentrations. However, more studies on the effects of oligosaccharide supplementation on insulin dysregulation are needed to improve the dietary management of horses with Equine Metabolic Syndrome.

Kinetics of Glucoregulatory Peptide Hormones during Hemodialysis with Cellulose Triacetate and Polysulfone Dialyzers in Patients with Diabetes and End-Stage Kidney Disease.

The mechanisms behind reported decreases in plasma insulin and glucagon during hemodialysis (HD) are not clear. Here, we investigated these mechanisms during HD treatment and the characteristics of insulin and glucagon removal when using two super high-flux membranes. In an experimental study, clearance, adsorption rates, and reduction rates of insulin and glucagon were investigated when using cellulose triacetate (CTA) and polysulfone (PS) membranes in a closed circuit using bovine blood. In a clinical study, 20 diabetes patients with end-stage kidney disease who were stable on HD were randomly selected for two HD sessions with two different membranes. At 1 h after the initiation of HD, insulin and glucagon clearance were measured, and the reduction rates were also investigated. In the experimental study, the PS membrane showed significantly higher clearance, adsorption rates, and reduction rates of insulin and glucagon compared with the CTA membrane. Although glucagon was detected in the ultrafiltration fluids in both membranes, insulin was absent in the PS membrane. In the clinical study, both membranes showed significant reductions in plasma insulin and glucagon at each time point. The PS membrane showed significantly higher insulin clearance and reduction rates compared with the CTA membrane. The two membranes showed no significant difference in glucagon clearance, but the glucagon reduction rate was significantly higher with the PS membrane. Our findings show that HD with the two super high-flux membranes used removes significant amounts of glucoregulatory peptide hormones from plasma in patients with diabetes and end-stage kidney disease, potentially affecting their glucose metabolism.

85-OR: Swi/Snf Controls Transcriptional Programs Required for ß-Cell Development and Postnatal Islet Function

A key feature of diabetes is insufficient functional β-cell mass. Strategies to augment functional β-cell mass include directed differentiation of stem cells towards a β-cell fate, which requires extensive knowledge of transcriptional programs governing differentiation in vivo. Pdx1, an essential transcription factor involved in β-cell differentiation, dynamically recruits coregulators to drive different gene expression programs. A recent study identified the ATP-dependent Swi/Snf chromatin remodeling complex as an important Pdx1-interacting partner. In the developing pancreas, conditional removal of the Brg Swi/Snf ATPase subunit compromised final pancreas mass, and loss of both ATPase subunits, Brg1 and Brm, led to glucose dyshomeostasis. While Swi/Snf is essential during early pancreas development and mature β-cell function, the role of Swi/Snf during endocrine cell development has yet to be explored. Here, we generated a conditional knockout of either Brg1 (Brg1ΔendoBrm+/-), Brm (Brg1Δendo/+Brm-/-), or both subunits (DKOΔendo) during endocrine development using Neurogenin 3 Cre. Four-week-old Brg1ΔendoBrm+/- mice are glucose intolerant, hyperglycemic, and hypoinsulinemic, with no phenotype observed in Brg1Δendo/+Brm-/-mice. Impaired glucose homeostasis of Brg1ΔendoBrm+/- mice was due in part to reduced islet number, impaired insulin secretion, and altered gene expression programs. DKOΔendo mice have not been found at weaning; however, postnatal day 6 DKOΔendo mice are severely hyperglycemic with reduced plasma insulin levels. Single-cell RNA-Seq of embryonic day 15.5 lineage-labeled cells revealed reduced insulin and glucagon transcript in the β-cell and α-cell clusters, respectively, in both Brg1ΔendoBrm+/- and DKOΔendo mice and reduced Neurogenin 3­ transcript in DKOΔendo endocrine progenitor clusters. These data suggest Swi/Snf plays a critical role in governing gene-expression programs essential for endocrine cell development. Disclosure R.K.Davidson: Employee; Eli Lilly and Company. S.Kanojia: None. M.E.Osmulski: None. J.Spaeth: None. Funding National Institutes of Health (R01DK129287, R03DK127129)

81-OR: The Rnf20 Ubiquitin Ligase Is Required for Beta-Cell Identity and Function

Type 1 and Type 2 Diabetes are characterized by a loss of functional β-cell mass. With the incidence of diabetes rising globally, a better understanding of the gene regulatory mechanisms maintaining β-cell functional identity is imperative to improve diabetes therapies. Islet 1 (Isl1) is a LIM-homeodomain class transcription factor that is essential for β-cell maturation and function. Our previous Isl1 studies revealed that it interacts with the histone ubiquitin ligases Ring Finger 20 (Rnf20) and Rnf40 in mouse β-cells, mouse islets, and human islets. Rnf20 and Rnf40 act as homo- or heterodimeric complexes wherein they monoubiquitinate histone 2B to regulate transcription. In mouse β-cell lines, we demonstrated that Rnf20 and Rnf40 are important for β-cell gene expression and insulin secretion, perhaps mediated by their occupancy of Slc2a2 and MafA. Additionally, using proximity ligation assay we showed a robust increase in Isl1 and Rnf20 interactions under high glucose conditions. Based on these findings, we hypothesized that at least Rnf20 is required for β-cell function in adult islets. To evaluate the contribution of Rnf complexes to β-cell maintenance, we developed an adult-inducible Rnf20 β-cell-specific knockout mouse model, termed Rnf20Δβ-cell. By 8 weeks of age (2 weeks after tamoxifen induction) male and female Rnf20Δβ-cell mice became hyperglycemic, severely glucose intolerant, and had reduced plasma insulin levels following a glucose challenge. Additionally, Rnf20Δβ-cell mice had reduced β-cell mass, in parallel with dysregulated expression of glucose-stimulated insulin secretion and β-cell identity mRNAs including Ins I, Slc2a2, Ucn3, Ngn3, and Aldh1a3. Our in vivo findings resemble those observed in adult Isl1 knockout mice. Paired with similar changes in gene expression in the Rnf20 and Isl1 models, and the glucose-responsive interaction between Isl1 and Rnf20 in vitro, our data support the hypothesis that Isl1-Rnf complexes are critical regulators of β-cell function. Disclosure T.Pierre: None. Y.Liu: None. C.S.Hunter: None. Funding National Institutes of Health (DK111483, DK128132)

Investigating the efficacy and feasibility of using a whole-of-diet approach to lower circulating levels of C-reactive protein in postmenopausal women: a mixed methods pilot study.

Chronic inflammation is associated with obesity and is an underlying pathophysiology for cardiovascular disease (CVD) development in postmenopausal women. This study aims to determine feasibility and efficacy of an anti-inflammatory dietary intervention to lower levels of C-reactive protein in weight stable postmenopausal women with abdominal obesity. This mixed-methods pilot study used a single arm pre-post design. Thirteen women followed a 4-week anti-inflammatory, dietary intervention, optimizing consumption of healthy fats, low glycemic index wholegrains, and dietary antioxidants. Quantitative outcomes included change in inflammatory and metabolic markers. Focus groups were undertaken and thematically analyzed to explore participants lived experience of following the diet. There was no significant change in plasma high-sensitivity C-reactive, protein. Despite discouraging weight loss, median (Q1-Q3) body weight decreased by -0.7 (-1.3 to 0 kg, P = 0.02). This was accompanied by reductions in plasma insulin (0.90 [-0.05 to 2.20] mmol/L), Homeostatic Model Assessment of Insulin Resistance (0.29 [-0.03 to 0.59]), and low-density lipoprotein:high-density lipoprotein ratio (0.18 [-0.01 to 0.40]) ( P ≤ 0.023 for all). Thematic analysis revealed that postmenopausal women have a desire to improve meaningful markers of health status that do not focus on weight. Women were highly engaged with learning about emerging and innovative nutrition topics, favoring a detailed and comprehensive nutrition education style that challenged their proficient health literacy and cooking skills. Weight-neutral dietary interventions targeting inflammation can improve metabolic markers and may be a viable strategy for CVD risk reduction in postmenopausal women. To determine effects on inflammatory status, a fully powered and longer-term randomized controlled trial is required.

RF04 | PSUN133 Assessment of the Rnf20 Histone Modifier in Regulating Pancreatic Beta-Cell Identity and Function

Abstract Type 1 and Type 2 Diabetes are characterized by a loss of functional pancreatic islet β-cells. With the prevalence of diabetes increasing worldwide, a complete understanding of the gene regulatory mechanisms governing the development and function of insulin-producing β-cells is requisite for improving diabetes therapies. Islet 1 (Isl1) is a LIM-homeodomain class transcription factor (TF) required for the maturation, proliferation, function, and survival of islet cells. In our previous study, we identified Isl1 interactions with the ring finger ubiquitin ligases Ring Finger 20 (Rnf20) and Rnf40 in mouse β-cell extracts, mouse islets, and human islets. Rnf20 and Rnf40, exist as homodimeric or heterodimeric complexes to deposit a mono-ubiquitin epigenetic mark on histone (H)2B (i.e., H2Bub1) and regulate gene transcription as a precursor to active H3K4 trimethylation (H3K4me3) and H3K79 methylation (H3K79me) marks. We demonstrated that Rnf20 and Rnf40 are required for the expression of several important β-cell genes and glucose-stimulated insulin secretion in vitro. Specifically, loss of Rnf20and Rnf40 in MIN6 β-cells resulted in a significant dysregulation of β-cell Slc2a2/Glut2 and MafA expression, target genes which were occupied by Rnf20 and H2Bub1. Additionally, using proximity ligation assay (PLA) in MIN6 β-cells, we demonstrated a robust increase in interactions between Isl1 and Rnf20 under high glucose conditions. Based on this, we hypothesize that Rnf20 and/or Rnf40 are required to establish and maintain β-cell identity in adult islets. To begin addressing this, we disrupted Rnf20/Rnf20 and/or Rnf20/Rnf40 complexes in β-cells via generation of adult inducible Rnf20 β-cell-specific knockout mice. In the adult inducible model, 2 weeks following tamoxifen induction (i.e., by 8 weeks of age) both male and female mice became hyperglycemic and severely glucose intolerant. These 8-week-old Rnf20-deficient mice also had reduced plasma insulin following a glucose challenge yet normal insulin sensitivity. Islet RNA exhibited dysregulated mRNAs encoding islet hormones, glucose-stimulated insulin secretion markers, and β-cell identity markers, including Slc2a2/Glut2, Ucn3, and Hb9 . Our findings of similar phenotypes between Isl1 and Rnf20 adult knockout models, a glucose sensitive interaction between Isl1 and Rnf20, and their occupancy of the Slc2a2/Glut2 locus support mechanisms of Isl1-Rnf driven β-cell regulation. Presentation: Saturday, June 11, 2022 1:12 p.m. - 1:17 p.m., Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m.

Sex-specific differences in metabolic outcomes after sleeve gastrectomy and intermittent fasting in obese middle-aged mice.

Despite the high prevalence of obesity among middle-aged subjects, it is unclear if sex differences in middle age affect the metabolic outcomes of obesity therapies. Accordingly, in this study, middle-aged obese female and male mice were randomized to one of three groups: sleeve gastrectomy (SG), sham surgery ad libitum (SH-AL), or sham surgery with weight matching to SG through intermittent fasting with calorie restriction (SH-IF). Comprehensive measures of energy and glucose homeostasis, including energy intake, body weight, energy expenditure, glucose and insulin tolerance, and interscapular brown adipose tissue (iBAT) sympathetic innervation density were obtained. At the end of 8 wk, SG and SH-IF females had better metabolic outcomes than their male counterparts. SG females had improved weight loss maintenance, preservation of fat-free mass (FFM), higher total energy expenditure (TEE), normal locomotor activity, and reduced plasma insulin and white adipose tissue (WAT) inflammatory markers. SH-IF females also had lower plasma insulin and WAT inflammatory markers, and higher TEE than SH-IF males, despite their lower FFM. In addition, SH-IF females had higher iBAT sympathetic nerve density than SG and SH-AL females, whereas there were no differences among males. Notably, SH-IF mice of both sexes had the most improved glucose tolerance, highlighting the benefits of fasting, irrespective of weight loss. Results from this study demonstrate that in middle-aged obese mice, female sex is associated with better metabolic outcomes after SG or IF with calorie restriction. Clinical studies are needed to determine if sex differences should guide the choice of obesity therapies.NEW & NOTEWORTHY SG or IF with calorie restriction produces better metabolic outcomes in females than in males. IF with calorie restriction prevents metabolic adaptation, even in the face of fat-free mass loss. IF with calorie restriction in females only, is associated with increased iBAT sympathetic innervation, which possibly mitigates reductions in energy expenditure secondary to fat-free mass loss. Lastly, IF leads to better glucose homeostasis than SG, irrespective of sex.

257-LB: A Novel MODY-Associated Gain-of-Function Mutation in TALK-1 Leads to Islet Dysfunction and Glucose Intolerance

The most islet-restricted and abundantly expressed K+ channel of the human ꞵ-cell, TALK-1, regulates electrical activity and glucose-stimulated insulin secretion (GSIS) . Recently we identified a gain-of-function (GOF) mutation near the pore domain of TALK-1 (Leu114Pro) that causes Maturity-Onset Diabetes of the Young (MODY) in an autosomal dominant manner, but only in a single family. To confirm TALK-1-Leu114Pro as the mutation that causes the MODY phenotype and investigate the impact of TALK-1 GOF on glucose homeostasis, a mouse model containing the TALK-1-Leu114Pro mutation was generated. Interestingly, mice with TALK-1-Leu114Pro mutation show neonatal lethality which may be due to alterations of islet hormone secretion during neonatal development (this was observed in heterozygous TALK-1-Leu114Pro C57BL/6J and homozygous TALK-1-Leu114Pro CD-1 (ICR) mice) . We first confirmed that TALK-1-Leu114Pro mutation resulted in a GOF in β-cell whole-cell K+ currents. On the ꞵ-cell plasma membrane the resulting TALK-1-Leu114Pro hyperpolarizing current blunted glucose-stimulated Ca2+ entry and subsequent Ca2+ oscillations, whereas on the endoplasmic reticulum membrane TALK-1-Leu114Pro enhanced IP3-induced Ca2+ release. TALK-1-Leu114Pro+/- islets also showed decreased GSIS and reduced plasma insulin levels in TALK-1-Leu114Pro+/- mice when compared to controls. TALK-1-Leu114Pro+/- mice exhibit a significant impairment in glucose homeostasis which is likely due to reduced islet Ca2+ influx and GSIS. However, TALK-1 activity in other islet cell types may also contribute to glucose dyshomeostasis in TALK-1-Leu114Pro+/- mice. For example, pancreatic α-cell area and islet glucagon secretion are increased TALK-1-Leu114Pro+/- mice. Taken together, these data prove that the MODY-associated TALK-1-Leu114Pro mutation disrupts glucose homeostasis and suggests that TALK-1 is an islet-restricted target for the treatment for diabetes. Disclosure A. Y. Nakhe: None. P. Dadi: None. K. E. Zaborska: None. D. Jacobson: None.

Treatment with rapamycin reduces progressive proteinuria while inducing hyperglycemia in obese Dahl salt‐sensitive leptin‐receptor mutant rats prior to puberty

Prepubertal obesity (PPO) is now considered a risk factor for the development of proteinuria and renal injury in children. Recently, we observed the early development of renal injury in the obese SSLepRmutant strain is associated with elevations in GFR and glomerular injury prior to puberty. However, the mechanisms involved remain unclear. The mammalian target of rapamycin (mTOR) signaling pathway has been shown to contribute to various forms of renal disease. In the current study, we examined whether treatment with the mTOR inhibitor, rapamycin, reduces the early progression of renal injury in SSLepRmutant rats during PPO. Four week‐old SS and SSLepRmutant rats were treated with either vehicle (saline) or rapamycin (1.5 mg/kg/day, ip) until rats reached 8 weeks of age. At baseline, body weight was significantly higher in vehicle‐treated SSLepRmutant rats compared to SS rats and remained elevated over the course of the study (309±13 vs. 219±27 g, respectively). Treatment with rapamycin significantly reduced body weight in SSLepRmutant rats compared to vehicle SSLepRmutant rats (206±9 g). At baseline, non‐fasting blood glucose levels were similar in both SS and SSLepRmutant rats and were within normal physiological range (≤120 mg/dl). Interestingly, chronic treatment with rapamycin markedly increased blood glucose levels in SSLepRmutant rats vs. vehicle SSLepRmutant rats (438±8 vs. 123±5 mg/dl, respectively) but had no effects in SS rats. At the end of the study, plasma insulin levels were significantly elevated in vehicle‐treated SSLepRmutant rats compared to the values measured in SS rats (6±1 vs. 1±0.6 ng/dl, respectively), and rapamycin treatment only reduced plasma insulin in SSLepRmutant (2±0.7 ng/dl, respectively). At baseline, proteinuria was significantly higher in SSLepRmutant rats compared to SS rats (159±34 and 17±7 mg/day, respectively) and remained elevated throughout the study (558±79 and 73±34 mg/day, respectively). By the end of the study, rapamycin significantly reduced proteinuria in SSLepRmutant rats (225±67 mg/day). We observed a significant increase in creatinine clearance (CCr) in SSLepRmutant rats vs SS rats indicating increased GFR (4.0±0.6 vs. 0.9±0.1 ml/min, respectively). Chronic treatment with rapamycin significantly decreased CCr in SSLepRmutant rats (2.2±0.9 ml/min) while not affecting SS rats. Overall, these data suggest that treatment with rapamycin is effective in reducing progressive proteinuria via reducing GFR while reducing plasma insulin levels and contributing to hyperglycemia in obese SSLepRmutant rats.

Decreasing Insulin Resistance Reduces Early Progressive Proteinuria by Decreasing Renal Hyperfiltration and Inflammation in Obese Dahl Salt‐Sensitive Rats

Prepubertal/childhood obesity (PPO) is quickly becoming an epidemic and is considered a major risk factor for proteinuria. Previous studies have demonstrated that insulin resistance alters renal hemodynamics leading to inflammation and renal injury in obese adults. However, studies examining the relationship between insulin resistance and renal hyperfiltration (RH) and inflammation in obese children are lacking. Recently, we reported that insulin resistance in the obese Dahl salt‐sensitive leptin receptor mutant (SSLepRmutant) rat is associated with progressive proteinuria and RH prior to puberty. Therefore, the aim of the present study was to examine whether decreasing insulin resistance with metformin will reduce proteinuria in SSLepRmutant rats. Four‐week‐old SS and SSLepRmutant rats were separated into 4 groups (n=5/group) and treated with either vehicle (PBS) or metformin (300 mg/kg/day, ip) for 4 weeks. Blood glucose levels were similar among the groups throughout the study (≤ 120 mg/dL). However, at the end of study, plasma insulin levels were significantly elevated in SSLepRmutant rats vs SS rats (9±2 vs 1±0.2 ng/ml respectively; p&lt;0.05), and glucose tolerance was significantly impaired in SSLepRmutant rats compared to values measured in SS rats. Chronic treatment with metformin markedly reduced plasma insulin (2±1 ng/ml; p&lt;0.05) and improved glucose tolerance in SSLepRmutant rats. At baseline, proteinuria was significantly higher in SSLepRmutant rats vs SS rats and remained elevated throughout the study (449±123 vs 25±7 mg/day, respectively; p&lt;0.05). Metformin treatment significantly decreased proteinuria in SSLepRmutant rats (177±80 mg/day; p&lt;0.05) with no effect in SS rats (36±13 mg/day). We observed a significant increase in creatinine clearance (CCr) in SSLepRmutant rats vs SS rats indicating RH (3.3±0.4 ml/min vs 1.9±0.1 ml/min, respectively; p&lt;0.05). Chronic treatment with metformin significantly decreased CCr in SSLepRmutant rats (1.3±0.2 ml/min; p&lt;0.05) while not affecting SS rats. Renal histology revealed marked glomerular injury in vehicle‐treated SSLepRmutant compared to SS rats, and treatment with metformin reduced glomerular injury in SSLepRmutant rats. We observed a significant increase in the renal infiltration of stimulatory dendritic cells and macrophages in vehicle‐treated SSLepRmutant rats compared to their SS counterparts, and metformin reduced the infiltration of these immune cells only in SSLepRmutant rats. MIP3α (pro‐inflammatory cytokine) was significantly increased and IL‐4 (anti‐inflammatory cytokine) was markedly decreased in the kidneys of SSLepRmutant rats compared to their SS counterparts (23±3 vs 5±1 ng/mg and 11±2 vs 54±5 ng/mg, respectively; p&lt;0.05). Treatment with metformin decreased renal MIP3α (10±2 ng/mg; p&lt;0.05), while increasing renal IL‐4 (26±5 ng/mg) in SSLepRmutant rats. These data suggest that decreasing insulin resistance reduces RH, proteinuria, and inflammation and may be therapeutically useful in managing renal injury during PPO.

Central deficiency of IL-6Ra in mice impairs glucose-stimulated insulin secretion

ObjectiveIL-6 is an important contributor to glucose and energy homeostasis through changes in whole-body glucose disposal, insulin sensitivity, food intake and energy expenditure. However, the relative contributions of peripheral versus central IL-6 signaling to these metabolic actions are presently unclear. A conditional mouse model with reduced brain IL-6Ra expression was used to explore how blunted central IL-6 signaling alters metabolic status in lean and obese mice. MethodsTransgenic mice with reduced levels of central IL-6 receptor alpha (IL-6Ra) (IL-6Ra KD mice) and Nestin Cre controls (Cre+/- mice) were fed standard chow or high-fat diet for 20 weeks. Obese and lean mouse cohorts underwent metabolic phenotyping with various measures of energy and glucose homeostasis determined. Glucose-stimulated insulin secretion was assessed in vivo and ex vivo in both mouse groups. ResultsIL-6Ra KD mice exhibited altered body fat mass, liver steatosis, plasma insulin, IL-6 and NEFA levels versus Cre+/- mice in a diet-dependent manner. IL-6Ra KD mice had increased food intake, higher RER, decreased energy expenditure with diminished cold tolerance compared to Cre+/- controls. Standard chow-fed IL-6Ra KD mice displayed reduced plasma insulin and glucose-stimulated insulin secretion with impaired glucose disposal and unchanged insulin sensitivity. Isolated pancreatic islets from standard chow-fed IL-6Ra KD mice showed comparable morphology and glucose-stimulated insulin secretion to Cre+/- controls. The diminished in vivo insulin secretion exhibited by IL-6Ra KD mice was recovered by blockade of autonomic ganglia. ConclusionsThis study shows that central IL-6Ra signaling contributes to glucose and energy control mechanisms by regulating food intake, energy expenditure, fuel flexibility and insulin secretion. A plausible mechanism linking central IL-6Ra signaling and pancreatic insulin secretion is through the modulation of autonomic output activity. Thus, brain IL-6 signaling may contribute to the central adaptive mechanisms engaged in response to metabolic stress.

Essential Amino Acid-Enriched Diet Alleviates Dexamethasone-Induced Loss of Muscle Mass and Function through Stimulation of Myofibrillar Protein Synthesis and Improves Glucose Metabolism in Mice.

Dexamethasone (DEX) induces dysregulation of protein turnover, leading to muscle atrophy and impairment of glucose metabolism. Positive protein balance, i.e., rate of protein synthesis exceeding rate of protein degradation, can be induced by dietary essential amino acids (EAAs). In this study, we investigated the roles of an EAA-enriched diet in the regulation of muscle proteostasis and its impact on glucose metabolism in the DEX-induced muscle atrophy model. Mice were fed normal chow or EAA-enriched chow and were given daily injections of DEX over 10 days. We determined muscle mass and functions using treadmill running and ladder climbing exercises, protein kinetics using the D2O labeling method, molecular signaling using immunoblot analysis, and glucose metabolism using a U-13C6 glucose tracer during oral glucose tolerance test (OGTT). The EAA-enriched diet increased muscle mass, strength, and myofibrillar protein synthesis rate, concurrent with improved glucose metabolism (i.e., reduced plasma insulin concentrations and increased insulin sensitivity) during the OGTT. The U-13C6 glucose tracing revealed that the EAA-enriched diet increased glucose uptake and subsequent glycolytic flux. In sum, our results demonstrate a vital role for the EAA-enriched diet in alleviating the DEX-induced muscle atrophy through stimulation of myofibrillar proteins synthesis, which was associated with improved glucose metabolism.

Tyramine exerts hypolipidemic and anti-obesity effects in vivo

Obesity and dyslipidemia are conditions often associated with cardiovascular risk, inflammation, oxidative stress, and death. Thus, a new approach has been highlighted to promote research and development of pharmacological tools derived from natural sources. Among the most widely studied groups of substances, polyphenols such as tyramine stand out. This study investigated hypolipidemic and anti-obesity properties of tyramine. Oral toxicity evaluation, models of dyslipidemia and obesity were used. To induce dyslipidemia, Poloxamer-407 (P-407) was administered intraperitoneally. In the hypercholesterolemic and obesity model, specific diet and oral tyramine were provided. After 24h of P-407 administration, tyramine 2 mg/kg (T2) decreased triglycerides (TG) (2057.0 ± 158.5 mg/dL vs. 2838 ± 168.3 mg/dL). After 48h, TG were decreased by T2 (453.0 ± 35.47 vs. 760.2 ± 41.86 mg/dL) and 4 mg/kg (T4) (605.8 ± 26.61 760.2 ± 41.86 mg/dL). T2 reduced total cholesterol (TC) after 24h (309.0 ± 11.17 mg/dL vs. 399.7 ± 15.7 mg/dL); After 48h, 1 mg/kg (T1) (220.5 ± 12.78 mg/dL), T2 (205.8 ± 7.1 mg/dL) and T4 (216.8 ± 12.79 mg/dL), compared to P-407 (275.5 ± 12.1 mg/dL). The treatment decreased thiobarbituric acid reactive substances and nitrite in liver, increased superoxide dismutase, reduced the diet-induced dyslipidemia, decreasing TC around 15%. Tyramine reduced body mass, glucose, and TC after hypercaloric feed. Treatment with 5 mg/L (0.46 ± 0.04 ng/dL) and 10 mg/L (0.44 ± 0.02 ng/dL) reduced plasma insulin (1.18 ± 0.23 ng/dL). Tyramine increased adiponectin at 5 mg/L (1.02 ± 0.02 vs. 0.83 ± 0.02 ng/mL) and 10mg/L (0.96 ± 0.04 ng/mL). In conclusion, tyramine has low toxicity in rodents, has antioxidant effect, reduces plasma triglycerides and cholesterol levels. However, further studies should be conducted in rodents and non-rodents to better understand the pharmacodynamic and pharmacokinetic properties of tyramine.

Reviewing physical exercise in non-obese diabetic Goto-Kakizaki rats.

There is a high incidence of non-obese type 2 diabetes mellitus (non-obese-T2DM) cases, particularly in Asian countries, for which the pathogenesis remains mainly unclear. Interestingly, Goto-Kakizaki (GK) rats spontaneously develop insulin resistance (IR) and non-obese-T2DM, making them a lean diabetes model. Physical exercise is a non-pharmacological therapeutic approach to reduce adipose tissue mass, improving peripheral IR, glycemic control, and quality of life in obese animals or humans with T2DM. In this narrative review, we selected and analyzed the published literature on the effects of physical exercise on the metabolic features associated with non-obese-T2DM. Only randomized controlled trials with regular physical exercise training, freely executed physical activity, or skeletal muscle stimulation protocols in GK rats published after 2008 were included. The results indicated that exercise reduces plasma insulin levels, increases skeletal muscle glycogen content, improves exercise tolerance, protects renal and myocardial function, and enhances blood oxygen flow in GK rats.