Peripheral Insulin Sensitivity Research Articles

Electroacupuncture improving obesity-induced insulin resistance via regulating intestinal SIRT1/TLR4 signaling pathway.

To observe the effect of electroacupuncture (EA) in obese rats with insulin resistance (IR) through regulating intestinal silent information regulator 1 (SIRT1)/Toll-like receptor 4 (TLR4) signaling pathway, so as to explore the underlying mechanism of EA in improving obesity-induced IR. A total of 40 Wistar rats were randomly divided into 4 groups, i.e. normal group, model group, EA group and EA combined with inhibitor group, with 10 rats in each group. The obesity-induced IR model was induced by feeding high-fat diet for 8 weeks. EA (2 Hz, 1mA) was applied at "Zhongwan"(CV12), "Guanyuan"(CV4), "Zusanli"(ST36) and "Fenglong" (ST40) for 10 min, 3 times a week for 8 weeks in both EA and EA combined with inhibitor groups. Sirtinol, an inhibitor of SIRT1 was injected into the tail vein (1 mg/kg), 3 times a week for 8 weeks in EA combined with inhibitor group. The body weight, glucose infusion rate (GIR) of rats in each group were recorded. The contents of serum C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and lipopolysaccharide (LPS) were detected by ELISA. Mucosal morphological changes in the small intestine was observed by HE staining and was graded using Chiu's score. The protein relative expression levels of SIRT1 and TLR4 and the co-labeling of SIRT1 with TLR4 in the small intestine was detected by Western blot and double immunofluorescence staining, separately. Compared with the normal group, the body weight, serum contents of CRP, TNF-α, IL-6, LPS, Chiu's score, TLR4 protein relative expression level and percentage of TLR4 positive expression area were increased (P<0.01, P<0.05), while the GIR, SIRT1 protein expression, percentage of SIRT1 positive expression area and SIRT1/TLR4 were decreased (P<0.01) in the model group. The pathological injury of small intestine mucosa was severe, accompanied with inflammatory cell infiltration in the model group. Following interventions, the body weight, serum contents of CRP, TNF-α and LPS, Chiu's score, TLR4 protein relative expression level and percentage of TLR4 positive expression area were decreased(P<0.01, P<0.05), and the GIR was increased (P<0.01), the pathological injury and inflammatory cell infiltration of small intestine mucosa were reduced in both EA and EA combined with inhibitor groups in contrast to the model group. Compared with the model group, the serum IL-6 content was significantly decreased (P<0.01), and the SIRT1 protein relative expression level and percentage of positive expression area, SIRT1/TLR4 were increased (P<0.01, P<0.05) in the EA group. Compared with the EA group, EA combined with inhibitor group showed the body weight, serum CRP, IL-6, LPS, Chiu's score, TLR4 protein relative expression level and TLR4 positive expression area were increased (P<0.01, P<0.05), and the GIR level , SIRT1 relative expression level, SIRT1/TLR4 ratio were decreased (P<0.05, P<0.01). EA can reduce the body weight and ameliorate peripheral insulin sensitivity in IR obese rats, which may be related with its function in regulating intestinal SIRT1/TLR4 signaling pathway to reduce inflammatory response.

Talin-1 inhibits Smurf1-mediated Stat3 degradation to modulate β-cell proliferation and mass in mice

Insufficient pancreatic β-cell mass and reduced insulin expression are key events in the pathogenesis of diabetes mellitus (DM). Here we demonstrate the high expression of Talin-1 in β-cells and that deficiency of Talin-1 reduces β-cell proliferation, which leads to reduced β-cell mass and insulin expression, thus causing glucose intolerance without affecting peripheral insulin sensitivity in mice. High-fat diet fed exerbates these phenotypes. Mechanistically, Talin-1 interacts with the E3 ligase smad ubiquitination regulatory factor 1 (Smurf1), which prohibits ubiquitination of the signal transducer and activator of transcription 3 (Stat3) mediated by Smurf1, and ablation of Talin-1 enhances Smurf1-mediated ubiquitination of Stat3, leading to decreased β-cell proliferation and mass. Furthermore, haploinsufficiency of Talin-1 and Stat3 genes, but not that of either gene, in β-cell in mice significantly impairs glucose tolerance and insulin expression, indicating that both factors indeed function in the same genetic pathway. Finally, inducible deletion Talin-1 in β-cell causes glucose intolerance in adult mice. Collectively, our findings reveal that Talin-1 functions as a crucial regulator of β-cell mass, and highlight its potential as a therapeutic target for DM patients.

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.

SAT415 Development Of A Novel, Preclinical Swine Model Of Transgender Men To Assess Testosterone Impact On Insulin Sensitivity And Whole-Body Metabolism

Abstract Disclosure: N. Mahabir: None. I. Ahmad: None. T. Wright: None. G. Ten Have: None. N. Deutz: None. A.E. Newell-Fugate: None. The effects oftestosterone therapy on peripheral insulin sensitivity in transgender men areequivocal due to heterogeneity of the population, short term patientfollow-up, and small cohort sizes. Most research has found testosterone therapyto decrease or have no effect on insulin sensitivity, but in one studytransgender men had increased insulin sensitivity. We have found thatshort-term, virilizing doses of testosterone in female pigs suppress circulatinginsulin levels. The objective of the current study was to develop a long-term,preclinical model of transgender men to assess insulin sensitivity and whole-bodymetabolism. A swine model of transgender men is superior to other models,because pigs closely mimic human cardiometabolic physiology and their largebody size permits longitudinal sampling and interventional procedures. Togenerate stable, long-term serum testosterone (TEST) concentrations in femalepigs, we fabricated testosterone silastic implants at the following doses:placebo (30 mm, n=1) or 15 mm (n=2), 30 mm (n=2), 60 mm (n=2), or 120 mm (n=1)TEST. Eight sexually mature female pigs were administered 14 days of progestin(Altrenogest) which was withdrawn on day 15. On day 16, 400 I.U. of pregnantmare serum gonadotropin and 200 I.U of human chorionic gonadotropin (PG600®,Merck Animal Health) were administered intramuscularly to stimulatefolliculogenesis and ovulation. Pigs had estrus detection performed dailythroughout the study and came into estrus 3-7 days post PG600® injection.Twenty-four hours post-estrus, implants were surgically placed subcutaneously,blood was taken, and biopsies of subcutaneous white adipose tissue werecollected from the incision site for baseline assessment of mitochondrialoxygen flux (Oroboros) and proteomic measurement of mitochondrial and insulinpathway abundance. After implant placement, fasted blood was collected at 24,48, 72 hours and every three days thereafter for six weeks. During weeks 2-6post-implantation, continuous glucose monitoring was performed (Freestyle Libre3). Twenty-four hours prior to study completion, a catheter was placed in thecranial vena cava and an intravenous glucose tolerance test was performed (0,5, 10, 20, 30, 40, 50, 60 min). The next morning fasted blood was collected (time0) and a stable isotopic tracer bolus was administered to measure whole bodyproduction of glycerol, branched chain amino acids, branched chain keto acids, and β-hydroxyβ-methylbutyric acid. After tracer bolus, blood was collected at 10, 20, 40, 60and 120 minutes. At 120 minutes post-bolus, tissues were collected for isotopiccompound measurement, mitochondrial function assays, and insulin signalingpathway assessment. This translational swine model will help uncover themechanistic effects of testosterone therapy on insulin sensitivity and whole-bodymetabolism in female to male transitioning patients. Presentation: Saturday, June 17, 2023

OR18-04 Leptin Decreases Gluconeogenesis And Gluconeogenic Substrate Availability In Patients With Lipodystrophy

Abstract Disclosure: E. Quaye: None. S. Chacko: None. M. Startzell: None. R.J. Brown: Other; Self; Metreleptin for the study was donated by Amryt Pharma. Leptin is an adipocyte-derived hormone that signals overall energy sufficiency. In patients with lipodystrophy, treatment with recombinant leptin (metreleptin) improved measures of glycemia and decreased energy expenditure. We hypothesized that metreleptin in patients with lipodystrophy would decrease gluconeogenesis (GNG) and gluconeogenic substrates through improvements in peripheral and hepatic insulin sensitivity. We conducted a single-arm prospective study of metreleptin administration in 9 patients with lipodystrophy from 2013-2018. The main outcomes of this study were basal and insulin-mediated suppression of GNG, carbon sources for GNG (glycerol rate of appearance (Ra) measured with isotope tracers, and plasma alanine and lactate), palmitate Ra (a driver of GNG, measured with isotope tracers), and peripheral and hepatic insulin sensitivity (measured as glucose disposal during a hyperinsulinemic clamp, and % suppression of glucose Ra during the clamp, respectively). Peripheral insulin sensitivity increased 2-fold (by 115±134%; P=0.001) after 6 months of metreleptin. Hepatic insulin sensitivity increased from 61% to 81% after 6 months of metreleptin with a trend toward statistical significance (P=0.08; 6 months vs. baseline). Basal GNG decreased by 16±12%, from 12.4±3.9 to 10.9±2.6 µmol/kgLBM/min, after 2 weeks of metreleptin (P=0.02) but did not change after 6 months (P=0.2). Metreleptin increased insulin-mediated suppression of GNG during the hyperinsulinemic clamp from 73% at baseline to 91% after 2 weeks (P&amp;lt;0.002; 2 weeks vs. baseline), and 94% after 6 months (P&amp;lt;0.001; 6 months vs. baseline). Alanine was unchanged after 2 weeks of metreleptin (P=0.1) but decreased by 21±22% after 6 months (P=0.005). There was a positive correlation between alanine and GNG at baseline (r=0.8, P=0.01), 2 weeks (r=0.8, P=0.03) and 6 months (r=0.9, P=0.002). Lactate decreased by 20±18% after 2 weeks (P=0.014) and 21±24% (P=0.001) after 6 months of metreleptin. There was no significant decrease in glycerol or palmitate Ra after 2 weeks of metreleptin, but palmitate Ra decreased after 6 months (P=0.04). Metreleptin treatment in patients with lipodystrophy reduced basal GNG and increased insulin mediated suppression of GNG. Reduced GNG may be mediated by improved insulin sensitivity leading to reductions in alanine and lactate, which are carbon sources for GNG. Associations between alanine and GNG persisted after metreleptin, suggesting that potential therapeutic interventions to reduce protein turnover in insulin-resistant states may improve glucose homeostasis. Presentation: Saturday, June 17, 2023

THU312 The Type 1 Diabetes Susceptible LEW.1WR1 Rat Develops Insulin Resistance And Severe Non-alcoholic Fatty Liver Disease

Abstract Disclosure: S.T. Love-Rutledge: None. M. Wimalarathne: None. L.D. Mercado: None. A. Smiley: None. C. Apperson: None. Q.C. Vidal: None. A subpopulation of type 1 diabetes patients develop the pathophysiological parameters to be termed double diabetes. This patient population often develops obesity, non-alcoholic fatty liver disease, and other hallmarks of insulin resistance. The LEW.1WR1 rat is a type 1 diabetes susceptible rodent with hyperinsulinemia that has shown signs of fatty liver infiltration1,2. We hypothesized that LEW.1WR1 rats would develop insulin resistance and severe nonalcoholic fatty liver disease due to its increased circulating insulin and predisposition to autoimmune disease. LEW.1WR1 rats and Wistar Furth rats were used for the 18-week long experiment. Peripheral insulin sensitivity was evaluated using insulin tolerance tests at weeks 11 and 17 showing worsening insulin sensitivity as evidenced by the gradual slope compared to the steep slope of the Wistar Furth rats. HOMA-IR values support LEW.1WR1 rats develop worsening insulin sensitivity and are insulin resistant at week 23 of the experiment (2.613± 0.796, p &amp;lt; 0.0001). Terminal liver mass confirmed increased liver mass normalized to body mass and liver triglyceride levels suggested increased ectopic lid accumulation in the liver (Liver Mass 2.65% ±0.32 p = 0.0005 and triglyceride levels 192.8 ± 21.85 mg/dL, p = 0.034). The H&amp;E-stained digital liver slides were scored for liver ballooning, steatosis, and markers of inflammation. Fibrosis and terminal circulating cytokines were also measured to assess severity of condition. While both groups showed increased steatosis and injury ballooning, trichrome blue staining and inflammatory cytokines verify the severity of disease in the LEW.1WR1 rats. LEW rats have increased fibrosis area and high serum TNF-α, IFN-, MCP-1 levels. As hypothesized, we observed that LEW.1WR1 rats show characteristics of insulin resistance and malignant nonalcoholic fatty liver disease development.

Peripheral insulin resistance is early, progressive, and correlated with cachexia in Walker-256 tumor-bearing rats.

Insulin (INS) resistance is often found in cancer-bearing, but its correlation with cachexia development is not completely established. This study investigated the temporal sequence of the development of INS resistance and cachexia to establish the relationship between these factors in Walker-256 tumor-bearing rats (TBrats). INS hepatic sensitivity and INS resistance-inducing factors, such as free fatty acids (FFA) and tumor necrosis factor-α (TNF-α), were also evaluated. Studies were carried out on Days 2, 5, 8, and/or 12 after inoculation of tumor cells in rats. The peripheral INS sensitivity was assessed by theINS tolerance testand the INS hepatic sensitivity in in situ liver perfusion. TBrats with 5, 8, and 12 days of tumor, but not 2 days, showed decreased peripheral INS sensitivity (INS resistance), retroperitoneal fat, and body weight, compared to healthy rats, which were more pronounced on Day 12. Gastrocnemius muscle wasting was observed only on Day 12 of tumor. The peripheral INS resistance was significantly correlated (r = -.81) with weight loss. Liver INS sensitivity of TBrats with 2 and 5 days of tumor was unchanged, compared to healthy rats. TBrats with 12 days of tumor showed increased plasma FFA and increased TNF-α in retroperitoneal fat and liver, but not in the gastrocnemius, compared to healthy rats. In conclusion, peripheral INS resistance is early, starts along with fat and weight loss and before muscle wasting, progressive, and correlated with cachexia, suggesting that it may play an important role in the pathogenesis of the cachectic process in TBrats. Therefore, early correction of INS resistance may be a therapeutic approach to prevent and treat cancer cachexia.

Hepatic sialic acid synthesis modulates glucose homeostasis in both liver and skeletal muscle

ObjectiveSialic acid is a terminal monosaccharide of glycans in glycoproteins and glycolipids, and its derivation from glucose is regulated by the rate-limiting enzyme UDP-GlcNAc 2-epimerase/ManNAc kinase (GNE). Although the glycans on key endogenous hepatic proteins governing glucose metabolism are sialylated, how sialic acid synthesis and sialylation in the liver influence glucose homeostasis is unknown. Studies were designed to fill this knowledge gap. MethodsTo decrease the production of sialic acid and sialylation in hepatocytes, a hepatocyte-specific GNE knockdown mouse model was generated, and systemic glucose metabolism, hepatic insulin signaling and glucagon signaling were evaluated in vivo or in primary hepatocytes. Peripheral insulin sensitivity was also assessed. Furthermore, the mechanisms by which sialylation in the liver influences hepatic insulin signaling and glucagon signaling and peripheral insulin sensitivity were identified. ResultsLiver GNE deletion in mice caused an impairment of insulin suppression of hepatic glucose production. This was due to a decrease in the sialylation of hepatic insulin receptors (IR) and a decline in IR abundance due to exaggerated degradation through the Eph receptor B4. Hepatic GNE deficiency also caused a blunting of hepatic glucagon receptor (GCGR) function which was related to a decline in its sialylation and affinity for glucagon. An accompanying upregulation of hepatic FGF21 production caused an enhancement of skeletal muscle glucose disposal that led to an overall increase in glucose tolerance and insulin sensitivity. ConclusionThese collective observations reveal that hepatic sialic acid synthesis and sialylation modulate glucose homeostasis in both the liver and skeletal muscle. By interrogating how hepatic sialic acid synthesis influences glucose control mechanisms in the liver, a new metabolic cycle has been identified in which a key constituent of glycans generated from glucose modulates the systemic control of its precursor.

Tau Loss of Function, by Deletion or Aggregation, Contributes to Peripheral Insulin Resistance.

Several epidemiological data revealed an association between Alzheimer's disease (AD) and type 2 diabetes. Researchers concentrated on brain insulin resistance with little emphasis on the link between systemic insulin resistance and AD, despite the fact that the incidence of type 2 diabetes is higher in AD patients and that impairment in insulin signaling is a risk factor for AD. The goal of this study is to determine the role of systemic insulin resistance in the pathogenesis of Alzheimer's disease by evaluating the consequences of tau loss-of-function on peripheral insulin sensitivity. Primary hepatocytes isolated from transgenic mouse models (Tau KO, P301 L) and wild type mice (C57BL/6) were evaluated for their insulin sensitivity using glucose uptake assays as well as biochemical analysis of insulin signaling markers. Our data show that tau deletion or loss of function promotes peripheral insulin resistance as seen in primary hepatocytes isolated from Tau KO and P301 L mice, respectively. Furthermore, exposure of wild-type primary hepatocytes to sub-toxic concentrations of tau oligomers results in a dose-dependent inhibition of glucose uptake, associated with downregulation of insulin signaling. Tau oligomers-induced inactivation of insulin signaling proteins was rescued by inhibition of p38 MAPK, suggesting the involvement of p38 MAPK. This is the first study testing tau role in peripheral insulin resistance at the cellular level using multiple transgenic mouse models. Moreover, this study suggests that tau should be functional for insulin sensitivity, therefore, any loss of function by deletion or aggregation would result in insulin resistance.

Exercise ameliorates skeletal muscle insulin resistance by modulating GRK4-mediated D1R expression.

Exercise has been recommended as a nonpharmaceutical therapy to treat insulin resistance (IR). Previous studies showed that dopamine D1-like receptor agonists, such as fenoldopam, could improve peripheral insulin sensitivity, while antipsychotics, which are dopamine receptor antagonists, increased susceptibility to Type 2 diabetes mellitus (T2DM). Meanwhile, exercise has been proved to stimulate dopamine receptors. However, whether the dopamine D1 receptor (D1R) is involved in exercise-mediated amelioration of IR remains unclear. We found that the D1-like receptor antagonist, SCH23390, reduced the effect of exercise on lowering blood glucose and insulin in insulin-resistant mice and inhibited the contraction-induced glucose uptake in C2C12 myotubes. Similarly, the opposite was true for the D1-like receptor agonist, fenoldopam. Furthermore, the expression of D1R was decreased in skeletal muscles from streptozotocin (STZ)- and high-fat intake-induced T2DM mice, accompanied by increased D1R phosphorylation, which was reversed by exercise. A screening study showed that G protein-coupled receptor kinase 4 (GRK4) may be the candidate kinase for the regulation of D1R function, because, in addition to the increased GRK4 expression in skeletal muscles of T2DM mice, GRK4 transgenic T2DM mice exhibited lower insulin sensitivity, accompanied by higher D1R phosphorylation than control mice, whereas the AAV9-shGRK4 mice were much more sensitive to insulin than AAV9-null mice. Mechanistically, the up-regulation of GRK4 expression caused by increased reactive oxygen species (ROS) in IR was ascribed to the enhanced expression of c-Myc, a transcriptional factor of GRK4. Taken together, the present study shows that exercise, via regulation of ROS/c-Myc/GRK4 pathway, ameliorates D1R dysfunction and improves insulin sensitivity.

Brain insulin action on peripheral insulin sensitivity in women depends on menstrual cycle phase

Insulin action in the human brain modulates eating behaviour, whole-body metabolism and body fat distribution1,2. In particular, brain insulin action increases whole-body insulin sensitivity, but these studies were mainly performed in lean men3,4. Here we investigate metabolic and hypothalamic effects of brain insulin action in women with a focus on the impact of menstrual cycle (ClinicalTrials.gov registration: NCT03929419).Eleven women underwent four hyperinsulinemic–euglycemic clamps, two in the follicular phase and two in the luteal phase. Brain insulin action was introduced using nasal insulin spray5–7 and compared to placebo spray in a fourfold crossover design with change in glucose infusion rate as the primary endpoint. Here we show that during the follicular phase, more glucose has to be infused after administration of nasal insulin than after administration of placebo. This remains significant after adjustment for blood glucose and insulin. During the luteal phase, no significant influence of brain insulin action on glucose infusion rate is detected after adjustment for blood glucose and insulin (secondary endpoint). In 15 other women, hypothalamic insulin sensitivity was assessed in a within-subject design by functional magnetic resonance imaging with intranasal insulin administration8. Hypothalamus responsivity is influenced by insulin in the follicular phase but not the luteal phase.Our study therefore highlights that brain insulin action improves peripheral insulin sensitivity also in women but only during the follicular phase. Thus, brain insulin resistance could contribute to whole-body insulin resistance in the luteal phase of the menstrual cycle.

Abstract 029: Hypertensive Disorder Of Pregnancy Results In Loss Of Pancreatic Beta Cell Area In Female Rat Offspring Without Development Of Glucose Intolerance

Hypertensive disorders of pregnancy can result in increased risk for type 2 diabetes (T2D) in offspring. Reduced pancreatic beta cell area can also influence development of glucose intolerance or T2D. Using a rat model of reduced uterine perfusion pressure (RUPP) which leads to hypertension during pregnancy and intrauterine growth restriction, we previously demonstrated reduced beta cell area in female RUPP offspring vs Sham at embryonic day 19 persisting to postnatal day (PD)13. To determine if this alteration in beta cell area is associated with phenotypic changes in glucose handling as offspring mature, we assessed IPGTT (intraperitoneal glucose tolerance test), OGTT (oral glucose tolerance test) and ITT (insulin tolerance test) in PD14, PD28, 8 week and 6 month female offspring (n=5-11/group). Our results demonstrate no change in fasting blood glucose and no alteration in glucose handling with IP glucose administration at any age. However, peak glucose following oral glucose administration was significantly less in RUPP offspring at PD14 (196.3+/-8.6 mg/dl, RUPP; 218.3+/-9.5 mg/dl, Sham; p=0.05), PD28 (220.0+/-4.1 mg/dl, RUPP; 280.0+/-12.8 mg/dl, Sham; p&lt;0.05) and 6 months (139.6+/-3.8 mg/dl, RUPP; 150.9+/-4.5 mg/dl, Sham; p&lt;0.05) compared to Sham, suggesting the incretin effect on pancreas and non-pancreas tissues is more effective in controlling blood glucose in RUPP offspring vs Sham. In addition, the decrease in glucose level in response to insulin injection in ITT was significantly greater in RUPP offspring vs Sham at PD28 (58.9+/-5.0 mg/dl, RUPP; 78.3+/-8.9 mg/dl, Sham; p&lt;0.05) suggesting increased insulin sensitivity in non-pancreatic tissues in RUPP compared to Sham offspring. Our studies demonstrate female offspring of hypertensive pregnancies are not glucose intolerant by 6 months of age. Despite reduced pancreatic beta cell area in female RUPP offspring early in development, glucose handling was maintained and even improved after oral glucose challenge in older RUPP offspring. Overall, these data suggest that increased peripheral insulin sensitivity may reduce the demand for beta cell function, and our studies reinforce the idea that adverse pregnancy can have a lasting effect on development and function of the pancreas.

Leptin Decreases Gluconeogenesis and Gluconeogenic Substrate Availability in Patients With Lipodystrophy.

The effects of leptin, an adipocyte-derived hormone that signals overall energy sufficiency, can only be studied in leptin-deficient conditions. In patients with lipodystrophy, a rare disease and unique model of leptin deficiency, treatment with recombinant leptin (metreleptin) improves glycemia and decreases energy expenditure. We hypothesized that these improvements might be mediated by reduced gluconeogenesis (GNG), an energy-requiring process. To determine the effects of metreleptin on GNG and GNG substrates. This was a single-arm prospective study of metreleptin administration in 15 patients with lipodystrophy, 9 of whom had data on GNG (NIH, 2013-2018). We analyzed total GNG, insulin-mediated suppression of GNG, glycerol, palmitate, alanine, lactate, peripheral and hepatic insulin sensitivity, and markers of glycemia (eg, HbA1c, glucose, fasting insulin). Metreleptin administration decreased basal GNG, increased insulin-mediated suppression of GNG, and improved insulin sensitivity and markers of glycemic control. Metreleptin reduced carbon sources for GNG, including plasma alanine and lactate, and rate of appearance (Ra) of glycerol, and decreased Ra of palmitate, a driver of GNG. Glycerol and palmitate Ra correlated with GNG prior to but not during metreleptin administration. Alanine strongly correlated with GNG both before and during metreleptin administration. Metreleptin treatment in patients with lipodystrophy reduced GNG likely through decreased availability of carbon sources for gluconeogenesis, such as alanine, lactate, and glycerol. Associations between alanine and GNG persisted after metreleptin treatment while correlations with glycerol and palmitate Ra did not persist, suggesting reduced importance of lipolysis as a driver of GNG in the leptin-replete state.

Short-term strength exercise reduces the macrophage M1/M2 ratio in white adipose tissue of obese animals

Obesity can exacerbate the systemic inflammatory process, leading to increased infiltration of monocytes in white adipose tissue (WAT) and polarization of these cells into pro-inflammatory M1 macrophages, while reducing the population of anti-inflammatory M2 macrophages. Aerobic exercise has been shown to be effective in reducing the pro-inflammatory profile. However, the impact of strength training and the duration of training on macrophage polarization in the WAT of obese individuals have not been widely studied. Therefore, our aim was to investigate the effects of resistance exercise on macrophage infiltration and polarization in the epididymal and subcutaneous adipose tissue of obese mice. We compared the following groups: Control (CT), Obese (OB), Obese 7-day strength training (STO7d), and Obese 15-day strength training (STO15d). Macrophage populations were evaluated by flow cytometry: total macrophages (F4/80+), M1 (CD11c), and M2 (CD206) macrophages. Our results demonstrated that both training protocols improved peripheral insulin sensitivity by increasing AKT phosphorylation (Ser473). Specifically, the 7-day training regimen reduced total macrophage infiltration and M2 macrophage levels without altering M1 levels. In the STO15d group, significant differences were observed in total macrophage levels, M1 macrophages, and the M1/M2 ratio compared to the OB group. In the epididymal tissue, a reduction in the M1/M2 ratio was observed in the STO7d group. Overall, our data demonstrate that 15 days of strength exercise can reduce the M1/M2 ratio of macrophages in white adipose tissue.

133-OR: Insulin Dynamics across the Glucose Tolerance Spectrum in Youth with Obesity

Despite β-cell failure in youth with dysglycemia (DYSG) (IGT + T2D), fasting insulin concentrations are elevated. Here, we examined 1) metabolic clearance rate of insulin (MCRI) in youth with normal glucose tolerance (NGT) and DYSG, 2) racial/ethnic differences in insulin dynamics and 3) physical and metabolic correlates of MCRI. In 95 Black (B) + 111 White (W) youth, age 14.4 ± 2.0 [SD] yrs., BMI 34.7 ± 6.4 kg/m2, MCRI and peripheral insulin sensitivity (PIS) were calculated from the hyperinsulinemic-euglycemic clamp, 1st-phase insulin (1stPhI) from the hyperglycemic clamp, disposition index (DI=PIS x 1stPhI), % body fat by DXA, visceral adipose tissue (VAT) by MRI. In DYSG vs NGT, MCRI was lower (261.6 ± 11.9 vs 334.1 ± 8.5 ml/m2/min, p&amp;lt;0.001) and fasting insulin was higher (46.9 ± 4.4 vs 32.9 ± 1.2 μU/mL, p&amp;lt;0.001). In B vs W youth (Image), MCRI was lower driven by DYSG. Lower PIS, lower MCRI and higher 1stPhI were characteristics of B youth with DYSG vs W with equally impaired DI. In B and W youth, positive correlates of MCRI were PIS and DI and negative correlates were fasting insulin, % body fat and VAT. In conclusion, higher fasting insulin concentrations in DYSG despite a failing β-cell could be explained by decreased MCRI. Racial/ethnic contrast in insulin dynamics differs by glycemic status and is more pronounced in DYSG manifested by lower PIS and lower MCRI in B vs W youth with no difference in β-cell function relative to insulin sensitivity. Disclosure W.Cho: None. F.Bacha: Other Relationship; Takeda Pharmaceutical Co., Ltd., AstraZeneca. H.M.Tfayli: Other Relationship; Novo Nordisk, Research Support; Sanofi, Novartis. S.Lee: None. S.Michaliszyn: None. J.Kim: None. S.A.Arslanian: Advisory Panel; Novo Nordisk, Eli Lilly and Company, Consultant; Société des Produits Nestlé SA,, Other Relationship; Eli Lilly and Company, AstraZeneca, Research Support; Novo Nordisk, Eli Lilly and Company. Funding American Diabetes Association (7-08-JF-27 to S.L.); Eunice Kennedy Shriver National Institute of Child Health and Human Development (K24HD01357, R01HD27503); National Center for Advancing Translational Sciences (UL1TR000005); National Center for Research

302-OR: How Menstrual Cycle Impacts Brain Insulin Action—Results from Young Women

The human brain is an insulin-sensitive organ that modulates whole-body glucose metabolism and adiposity. In case of brain insulin resistance, this regulation is disturbed. In the periphery, insulin sensitivity varies along the menstrual cycle, while the effects on brain insulin action are still unknown. We here investigated the impact of menstrual cycle on brain insulin sensitivity of the human hypothalamus and on brain-derived modulation of peripheral metabolism. In 26 naturally cycling women (age 19-29 years, BMI 18-24 kg/m2), brain insulin action was assessed in both the follicular and the luteal phase using nasal application of 160 U insulin. In fifteen women, we assessed hypothalamic insulin responsiveness by functional MRI combined with nasal insulin. In eleven women, brain-derived modulation of peripheral insulin sensitivity was studied by hyperinsulinemic euglycemic clamps combined with insulin vs placebo spray. Only in the follicular phase, nasal insulin significantly decreased hypothalamic blood flow (p=0.02), indicating proper brain insulin action. In the luteal phase, insulin induced no such effect (p=0.6). During hyperinsulinemic euglycemic clamps in the follicular phase, more glucose had to be infused after insulin compared to placebo spray. This difference remained significant after adjustment for circulating glucose and insulin (p&amp;lt;0.0001), which was not the case in the luteal phase (p=0.1). High estradiol/progesterone ratio, as present during the follicular phase, was linked to a stronger effect of insulin spray on glucose infusion rates than placebo. Brain insulin sensitivity is a regulated process that can rapidly adapt to changing physiologic requirements, as through the menstrual cycle. In the luteal phase, we detected hypothalamic insulin resistance, which likely contributed to the lacking modulation of peripheral insulin sensitivity through brain insulin delivery. Thus, brain insulin resistance could contribute to whole-body insulin resistance in the luteal phase. Disclosure J.Hummel: None. M.Roden: Advisory Panel; Eli Lilly and Company, Consultant; TARGET PharmaSolutions, Inc., Research Support; Boehringer-Ingelheim, Novo Nordisk, Novartis, Sanofi. H.Häring: None. A.Fritsche: Advisory Panel; Novo Nordisk, Lilly, Sanofi, Boehringer-Ingelheim, Speaker's Bureau; AstraZeneca, SYNLAB Holding Deutschland GmbH. A.Peter: None. R.Wagner: Advisory Panel; Daiichi Sankyo, Speaker's Bureau; Novo Nordisk, Sanofi. S.Kullmann: None. M.Heni: Advisory Panel; Boehringer-Ingelheim, Sanofi, Research Support; Boehringer Ingelheim Inc., Speaker's Bureau; Lilly, Bayer Inc., Sanofi, Boehringer-Ingelheim, Novo Nordisk, Amryt Pharma Plc. C.Benkendorff: None. L.Fritsche: None. K.Prystupa: Other Relationship; Berlin-Chemie AG. A.Vosseler: None. S.Gancheva: Consultant; Novo Nordisk, Bayer Inc. S.Trenkamp: None. A.L.Birkenfeld: None. H.Preissl: None. Funding German Federal Ministry of Education and Research

347-OR: Methionine Restriction Differentially Protects against High-Fat Diet-Induced Neuroinflammation and Central Insulin Resistance in Male and Female Mice

High-fat diets (HFD) promote central inflammation and insulin resistance (IR). Methionine restriction (MR) improves peripheral insulin sensitivity, lipid metabolism, and cognitive function, at least in part by increasing fibroblast growth factor 21 (FGF21). However, the ability of MR to protect against neuroinflammation and central IR during adolescence has not been examined. Moreover, whether MR depends on FGF21 to protect against HFD-induced changes in central insulin signaling or neuroinflammation is unknown. We sought to determine whether MR protects against HFD-induced neuroinflammation and central IR during adolescence in males and females and whether MR’s effects are dependent on FGF21. Male and female wild-type (WT) and FGF21 knockout (KO) mice, aged 5 to 6 wk, were fed normal (18.9% fat-derived kcal) or high-fat (60% fat-derived kcal) versions of control (0.86% methionine) or MR (0.17% methionine) diets for 5 wk. To investigate insulin action, ITTs were performed after 4 wk on the diet, and saline or insulin (0.6U/kg body weight) was administered 15 min prior to sacrifice. MR significantly decreased weight gain of HFD-fed mice regardless of sex or genotype (p &amp;lt; 0.05). MR increased serum FGF21 of all males and HFD-fed females (p &amp;lt; 0.05), and strongly tended to increase FGF21 in female mice on the normal-fat diet. HFD feeding tended to promote inflammatory gene expression in the hippocampus of WT males, while MR trended to mitigate inflammation independent of FGF21. MR also significantly reduced fasting blood glucose and improved peripheral insulin response in an FGF21-dependent fashion (p &amp;lt; 0.05). Though, neither HFD nor MR had a notable impact on markers of IR in the hypothalamus or hippocampus. Our findings indicate that short-term MR improves metabolic parameters of adolescent mice fed normal or high-fat diets. In addition, MR acts in an FGF21-independent and sex-dependent manner to improve neuroinflammation. Disclosure H.L.Lail: None. R.Lawrence: None. D.Wanders: None.

191-OR: Deletion of the Type 2 Diabetes Candidate Gene SLC16A11 Reduces Peripheral Insulin Sensitivity in Mice

Background and Aims: Recent GWAS in large human populations identified the monocarboxylate transporter SLC16A11 as a candidate gene for T2D. While previous studies postulated that SLC16A11 plays a role in hepatic lipid and glucose metabolism, the existing data are controversial and exact mechanisms of how SLC16A11 affects T2D are missing. Here, we aimed at elucidating the role of SLC16A11 in the development of metabolic disease. Methods: HEK293 cell lines expressing murine and human SLC16A11 were established. Moreover, using CRISPR/Cas9, a SLC16A11 knockout mouse model was generated. Finally, SLC16A11 mRNA expression was measured in various insulin responsive tissues of ob/ob and db/db mice. Results: In HEK293 cells, substrates of the transporter were identified. mRNA expression of SLC16A11 was reduced in skeletal muscle of ob/ob and db/db mice (-69.8% and -22.8%; p&amp;lt;0.05) compared to littermate controls. SLC16A11 KO and WT littermate mice fed NCD or HFD did not differ in body weight and composition, energy expenditure or food intake. While basal glucose and insulin in SLC16A11 KO and WT littermates on a HFD were not different, glucose infusion rate during hyperinsulinemic euglycemic clamp was lower in SLC16A11 KO mice (SLC16A11 WT= 36.4±3 mg/kg/min; SLC16A11 KO= 24.7±2 mg/kg/min; P&amp;lt;0.01), indicating reduced whole-body insulin sensitivity. No changes were observed in hepatic glucose production, liver fat content or hepatic mitochondrial function using PINTA method. Instead, clamped 2-deoxy-glucose uptake was significantly reduced in skeletal muscle (-41%; p&amp;lt;0.05) of SLC16A11 KO, together with increased DAGs levels and PKCθ activation, indicating skeletal muscle insulin resistance. Conclusions: Our data show for the first time that in contrast to previous assumptions, SLC16A11 impairs skeletal muscle insulin sensitivity without affecting hepatic metabolism. Taking also human GWAS into account, we propose that SLC16A11 may be an interesting target for the treatment of T2D. Disclosure N.N.El-agroudy: None. T.Schumann: None. A.Kurzbach: None. G.Sancar: None. L.Sandforth: None. C.Herrmann: None. G.I.Shulman: Consultant; Novo Nordisk, DiCerna Pharmaceuticals, Inc., Bayer Consumer Care AG, Kriya Therapeutics, Arrowhead Pharmaceuticals, Inc., ESPERION Therapeutics, Inc., Other Relationship; AstraZeneca, Merck &amp; Co., Inc., Janssen Research &amp; Development, LLC, iMetabolic Biopharma Corporation, Maze Therapeutics, 89bio, Inc., Equator Therapeutics, Inc., Generian Pharmaceuticals, Fortress Biotech, Inc., OrsoBio, Aro Biotherapeutics Company, Stock/Shareholder; Levels Health, Inc. A.L.Birkenfeld: None.

363-OR: Brown Adipose Tissue m6A mRNA Methylation Regulates Systemic Insulin Sensitivity via a Prostaglandin Interorgan Axis

Brown adipose tissue (BAT) has the capacity to regulate peripheral insulin sensitivity via the secretion of signaling lipids. N6-methyladenosine (m6A) is among the most prevalent and abundant post-transcriptional RNA modifications in eukaryotes. Recently, m6A has been shown to regulate islet and hepatic metabolism as well as BAT adipogenesis and energy expenditure. Here, we demonstrate that deficiency of m6A methyltransferase-like 14 (M14) in BAT positively regulates BAT-secretory function to improve systemic insulin sensitivity through inter-organ communication. Using lipidomic approaches, we identified prostaglandin E2 (PGE2) and prostaglandin F2a (PGF2a) as M14KOBAT-secreted insulin sensitizers. Notably, circulatory PGE2 and PGF2a showed significant inverse correlation with HOMA-IR in humans. Furthermore, in vivo administration of PGE2 and PGF2a in HFD-induced insulin resistant obese mice recapitulated the phenotypes of M14KO mice. Exogenous PGE2 or PGF2a significantly improved insulin stimulated-pAKT by suppressing expression of specific phosphatases in human hepatocyte cell line. Mechanistically, M14-mediated m6A installation destabilizes transcripts encoding PGE2 and PGF2a synthases in brown adipocytes in an YTHDF2/3-dependent manner. Collectively, these results unveil a new mechanism by which m6A-facilitated BAT-secretory function enables the regulation of whole body insulin sensitivity. Disclosure L.Xiao: None. J.Pihlajamaki: None. Y.Tseng: Consultant; Cellarity, LyGenesis. R.Kulkarni: Advisory Panel; Novo Nordisk, Inversago, Biomea Fusion, Inc., REDD Pharma, Research Support; Inversago. D.F.De jesus: None. C.Ju: None. J.Wei: None. J.Hu: None. T.Tsuji: None. C.Cero: None. D.Kaminska: None. A.M.Cypess: None.

Interleukin 6 acutely increases gluconeogenesis and decreases the suppressive effect of insulin on cAMP-stimulated glycogenolysis in rat liver.

Interleukin 6 (IL6) is an multifunctional cytokine that modulates several biological responses, including glucose metabolism. However, its acute effects on hepatic glucose release are still uncertain. The main purpose of this study was to investigate the effects of IL6 on gluconeogenesis from several glucose precursors (alanine, pyruvate and glutamine) and on the suppressive action of insulin on cAMP-stimulated glycogen catabolism in rat liver. IL6 effect on insulin peripheral sensitivity was also evaluated. IL6 was injected intravenously into rats and, 1 h later, gluconeogenesis and glycogenolysis were assessed in liver perfusion and peripheral insulin sensitivity by insulin tolerance test (ITT). IL6 intravenous injection increased hepatic glucose production from alanine, without changing pyruvate, lactate and urea production. IL6 injection also increased hepatic glucose production from pyruvate and glutamine. In addition, IL6 decreased the suppressive effect of insulin on cAMP-stimulated glucose and lactate production and glycogenolysis, without affecting pyruvate production. Furthermore, IL6 reduced the plasma glucose disappearance constant (kITT), an indicator of insulin resistance. In conclusion, IL6 acutely increased hepatic glucose release (gluconeogenesis and glycogenolysis) by a mechanism that likely involved the induction of insulin resistance in the liver, as evidenced by the reduced suppressive effect of insulin on cAMP-stimulated glycogen catabolism. In consistency, IL6 acutely induced peripheral insulin resistance.