Impact Insulin Sensitivity Research Articles

Sustained caloric restriction potentiates insulin action by activating prostacyclin synthase.

Caloric restriction (CR) is known to enhance insulin sensitivity and reduce the risk of metabolic disorders; however, its molecular mechanisms are not fully understood. This study aims to elucidate specific proteins and pathways responsible for these benefits. We examined adipose tissue from participants in the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy Phase 2 (CALERIE 2) study, comparing proteomic profiles from individuals after 12 and 24 months of CR with baseline and an ad libitum group. Biochemical and cell-specific physiological approaches complemented these analyses. Our data revealed that CR upregulates prostacyclin synthase (PTGIS) in adipose tissue, an enzyme crucial for producing prostacyclin (PGI2). PGI2 improves the ability of insulin to stimulate the tether-containing UBX domain for GLUT4 (TUG) cleavage pathway, which is essential for glucose uptake regulation. Additionally, iloprost, a PGI2 analog, was shown to increase insulin receptor density on cell membranes, increasing glucose uptake in human adipocytes. CR also reduces carbonylation of GLUT4, a modification that is detrimental to GLUT4 function. CR enhances insulin sensitivity by promoting PTGIS expression and stimulating the TUG cleavage pathway, leading to increased GLUT4 translocation to the cell surface and decreased GLUT4 carbonylation. These findings shed light on the complex molecular mechanisms through which CR favorably impacts insulin sensitivity and metabolic health.

Oxidised phosphatidylcholine induces sarcolemmal ceramide accumulation and insulin resistance in skeletal muscle.

Intracellular ceramide accumulation in specific cellular compartments is a potential mechanism explaining muscle insulin resistance in the pathogenesis of type 2 diabetes. Muscle sarcolemmal ceramide accumulation negatively impacts insulin sensitivity in humans, but the mechanism explaining this localised accumulation is unknown. Previous reports revealed that circulating oxidised LDL is elevated in serum of individuals with obesity and type 2 diabetes. Oxidised phosphatidylcholine, which is present in oxidised LDL, has previously been linked to ceramide pathway activation, and could contribute to localised ceramide accumulation in skeletal muscle. We hypothesised that oxidised phosphatidylcholine inversely correlates with insulin sensitivity in serum, and induces sarcolemmal ceramide accumulation and decreases insulin sensitivity in muscle. We used LC-MS/MS to quantify specific oxidised phosphatidylcholine species in serum from a cross-sectional study of 58 well-characterised individuals spanning the physiological range of insulin sensitivity. We also performed in vitro experiments in rat L6 myotubes interrogating the role of specific oxidised phosphatidylcholine species in promoting sarcolemmal ceramide accumulation, inflammation and insulin resistance in skeletal muscle cells. Human serum oxidised phosphatidylcholine levels are elevated in individuals with obesity and type 2 diabetes, inversely correlated with insulin sensitivity, and positively correlated with sarcolemmal C18:0 ceramide levels in skeletal muscle. Specific oxidised phosphatidylcholine species, particularly 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine (POVPC), increase total ceramide and dihydroceramide and decrease total sphingomyelin in the sarcolemma of L6 myotubes by de novo ceramide synthesis and sphingomyelinase activation. POVPC also increases inflammatory signalling and causes insulin resistance in L6 myotubes. These data suggest that circulating oxidised phosphatidylcholine species promote ceramide accumulation and decrease insulin sensitivity in muscle, help explain localised sphingolipid accumulation and muscle inflammatory response, and highlight oxidised phosphatidylcholine species as potential targets to combat insulin resistance.

KLF3 impacts insulin sensitivity and glucose uptake in skeletal muscle.

Skeletal muscle is one of the predominant sites involved in glucose disposal, accounting for approximately 80% of postprandial glucose uptake, and plays a critical role in maintaining glycemic homeostasis. Dysregulation of energy metabolism in skeletal muscle is involved in developing insulin resistance and type 2 diabetes (T2D). Transcriptomic responses of skeletal muscle to exercise found that the expression of Klf3 was increased in T2D Goto-Kakizaki (GK) rats and decreased after exercise with improved hyperglycemia and insulin resistance, implying that Klf3 might be associated with insulin sensitivity and glucose metabolism. We also found that knockdown of Klf3 promoted basal and insulin-stimulated glucose uptake in L6 myotubes, while overexpression of Klf3 resulted in the opposite. Through pairwise comparisons of L6 myotubes transcriptome, we identified 2256 and 1988 differentially expressed genes in Klf3 knockdown and overexpression groups, respectively. In insulin signaling, the expression of Slc2a4, Akt2, Insr and Sorbs1 was significantly increased by Klf3 knockdown and decreased with klf3 overexpression; Ptprf and Fasn were markedly downregulated in klf3 reduced group and upregulated in klf3 overexpressed group. Moreover, downregulation of Klf3 promoted the expression of GLUT4 and AKT proteins, as well as the translocation of GLUT4 to the cell membrane in the basal situation, and enhanced insulin sensitivity, characterized by increased insulin-stimulated GLUT4 translocation and AKT, TBC1D1 and TBC1D4 phosphorylation, while overexpression of Klf3 showed contrary results. These results suggest that Klf3 affects glucose uptake and insulin sensitivity via insulin signal transduction and intracellular metabolism, offering a novel potential treatment strategy for T2D.

ATP-binding cassette family C member 1 constrains metabolic responses to high-fat diet in male mice.

Glucocorticoids modulate glucose homeostasis, acting on metabolically active tissues such as liver, skeletal muscle, and adipose tissue. Intracellular regulation of glucocorticoid action in adipose tissue impacts metabolic responses to obesity. ATP-binding cassette family C member 1 (ABCC1) is a transmembrane glucocorticoid transporter known to limit the accumulation of exogenously administered corticosterone in adipose tissue. However, the role of ABCC1 in the regulation of endogenous glucocorticoid action and its impact on fuel metabolism has not been studied. Here, we investigate the impact of Abcc1 deficiency on glucocorticoid action and high-fat-diet (HFD)-induced obesity. In lean male mice, deficiency of Abcc1 increased endogenous corticosterone levels in skeletal muscle and adipose tissue but did not impact insulin sensitivity. In contrast, Abcc1-deficient male mice on HFD displayed impaired glucose and insulin tolerance, and fasting hyperinsulinaemia, without alterations in tissue corticosterone levels. Proteomics and bulk RNA sequencing revealed that Abcc1 deficiency amplified the transcriptional response to an obesogenic diet in adipose tissue but not in skeletal muscle. Moreover, Abcc1 deficiency impairs key signalling pathways related to glucose metabolism in both skeletal muscle and adipose tissue, in particular those related to OXPHOS machinery and Glut4. Together, our results highlight a role for ABCC1 in regulating glucose homeostasis, demonstrating diet-dependent effects that are not associated with altered tissue glucocorticoid concentrations.

The ASSIST trial: Acute effects of manipulating strength exercise volume on insulin sensitivity in obese adults: A protocol for a randomized controlled, crossover, clinical trial.

Type 2 diabetes mellitus is a disease in which insulin action is impaired, and an acute bout of strength exercise can improve insulin sensitivity. Current guidelines for strength exercise prescription suggest that 8 to 30 sets could be performed, although it is not known how variations in exercise volume impact insulin sensitivity. Additionally, this means an almost 4-fold difference in time commitment, which might directly impact an individual's motivation and perceived capacity to exercise. This study will assess the acute effects of high- and low-volume strength exercise sessions on insulin sensitivity. After being thoroughly familiarized, 14 obese individuals of both sexes (>40 year old) will undergo 3 random experimental sessions, with a minimum 4-day washout period between them: a high-volume session (7 exercises, 3 sets per exercise, 21 total sets); a low-volume session (7 exercises, 1 set per exercise, 7 total sets); and a control session, where no exercise will be performed. Psychological assessments (feeling, enjoyment, and self-efficacy) will be performed after the sessions. All sessions will be held at night, and the next morning, an oral glucose tolerance test will be performed in a local laboratory, from which indexes of insulin sensitivity will be derived. We believe this study will aid in strength exercise prescription for individuals who claim not to have time to exercise or who perceive high-volume strength exercise intimidating to adhere to. This trial was prospectively registered (ReBEC #RBR-3vj5dc5 https://ensaiosclinicos.gov.br/rg/RBR-3vj5dc5).

OR12-04 LEAP2 Deletion Does Not Counteract The Effects Of Ghrelin Deletion During Insulin-Induced-Hypoglycemia

Abstract Disclosure: K. Shankar: None. S. Varshney: None. D. Gupta: None. O. Singh: None. S.B. Ogden: None. S. Osborne-Lawrence: None. N.P. Metzger: None. C.P. Richard: None. J.M. Zigman: Grant Recipient; Self; Novo Nordisk. Objective: The hormones ghrelin and LEAP2 both are endogenous ligands for the growth hormone secretagogue receptor (GHSR). Whereas ghrelin activates GHSR, LEAP2 blocks ghrelin from activating GHSR and also inhibits GHSR constitutive activity. It is via GHSR that the glucoregulatory actions of ghrelin and LEAP2 are mediated. These glucoregulatory actions are highlighted by the findings of severe hypoglycemia in ghrelin-KO mice and LEAP2-overexpressing mice when they are submitted to an acute-on-chronic caloric restriction protocol. Also, recently, our group showed that ghrelin-KO mice require a much higher glucose infusion rate (GIR) and exhibit markedly reduced elevation of counterregulatory hormones when submitted to a hyperinsulinemic-hypoglycemic clamp. In the current study, we investigated the potential of LEAP2 to protect against insulin-induced-hypoglycemia and counteract the effects of ghrelin deletion during the hypoglycemic clamp. Methods: Eight-ten week-old male wild-type (WT), Ghrelin-KO, LEAP2-KO, and LEAP2/Ghrelin-doubleKO (lacking both ghrelin and LEAP2 ) littermates were used for this study (n=7-10 per genotype). Mice were implanted with a right jugular vein catheter. Five days later, hyperinsulinemic-hypoglycemic clamps were performed in conscious, unrestrained mice. A low dose of insulin was infused at 4 mU/kg/min i.v. over 2 hr. A 20% glucose solution was simultaneously infused at a variable rate to achieve hypoglycemia (35–45 mg/dL) during the final 30 min. Blood glucose was measured via tail nicks every 5 min. Results: We were able to achieve the target hypoglycemic range in all four genotypes using this protocol. As compared to WT mice, Ghrelin-KO mice required markedly elevated (∼110% higher) GIRs (10±4 mg/kg/min in WT vs. 22±2 mg/kg/min in Ghrelin-KO mice; p=0.03) by the end of the 2-hr clamp. The GIRs required by LEAP2-KO mice were equivalent to those of WT mice (7±2 mg/kg/min in LEAP2-KO; p=n.s.). Furthermore, although during the first 60 min of the clamp, LEAP2/Ghrelin-doubleKO mice exhibited slightly lower blood glucose levels than the other genotypes and during the middle 60 min of the clamp, they required higher GIRs than the other genotypes, by the end of the 2-hr clamp, their GIRs were similar to Ghrelin-KO mice (25±3 mg/Kg/min in Ghrelin/LEAP2-doubleKO mice, p=n.s.). Conclusions: These data suggest a complex effect of LEAP2 on blood glucose. Alone, LEAP2 deletion does not impact insulin sensitivity. When coupled with ghrelin deletion, LEAP2 deletion lowers fasting blood glucose and causes greater insulin sensitivity early on during the hyperinsulinemic-hypoglycemic clamp. By the end of the clamp, this effect of LEAP2 deletion when coupled to ghrelin deletion is gone. Altogether, these results suggest that LEAP2 deletion does not counteract the effects of ghrelin deletion during insulin-induced hypoglycemia. Presentation: Friday, June 16, 2023

134-OR: Associations of Growth Hormone (GH) Mediators with Loss of Glycemic Control in Youth with Type 2 Diabetes (T2D)

T2D in youth has a more severe phenotype than in adults, with puberty as a potential contributor to this difference. Pubertal changes in GH mediators (e.g., insulin-like growth factor 1 (IGF-1), growth hormone receptor (GHR), insulin-like growth factor binding protein 1 (IGFBP-1)) may impact insulin sensitivity and beta cell function. We examined associations of GH mediators with loss of glycemic control in youth with T2D using the Treatment Options for Type 2 Diabetes in Adolescents and Youth (TODAY) cohort (N= 310). We performed paired comparison of plasma concentrations of IGF-1, GHR, and IGFBP-1 (ELISA), between 0mo and 36mo based on TODAY primary outcome of loss of glycemic control vs. maintained glycemic control (LGC vs MGC), with LGC defined as HbA1c ≥ 8% for 6 months and/or insulin dependence. We studied associations of GH mediators with HbA1c, insulinogenic index, oral disposition index, and 1/fasting insulin. Models were adjusted for age, sex, race, treatment arm, and baseline HbA1c (linear regression). Mean plasma IGF-1 (ng/mL) was lower in LGC group at 0mo (LGC: 451 ± 141, MGC: 485 ± 155, p = 0.04), and at 36mo (LGC: 340 ± 117, MGC: 400 ± 136, p< 0.0001). Increase in IGF-1 between 0-36mo predicted lower HbA1c at 36mo (B = -3.2E-3, SE = 9.0E-4, p < 0.001). Higher GHR was associated with higher HbA1c (B = 1.2E-2, SE = 3.0E-3, p < 0.001) and lower 1/fasting insulin (B = -6.6E-4, SE = 2.1E-4, P < 0.01) at 0mo. Increase in GHR between 0-36mo predicted higher 36mo HbA1c (B = 3.0E-2, SE = 9.4E-3, p < 0.01). IGFBP-1 was positively associated with 1/fasting insulin at 0m (B = 1.1E-3, SE = 4.9E-4, p = 0.03). In exploratory analyses stratified by Tanner stage (TS) at study entry, GH mediators changed differentially between TS 1-3 (n = 31) vs TS 4-5 (n = 274). In conclusion, GH mediators differed based on primary outcome in TODAY, and were associated with HbA1c and insulin sensitivity. Whether changes in GH mediators contribute to, or are the result of, changes in glucose metabolism is a key area for future studies. Disclosure C.Lu: None. D.Wolfs: None. L.El ghormli: None. L.M.Laffel: Advisory Panel; Medtronic, Lilly Diabetes, Novo Nordisk, Vertex Pharmaceuticals Incorporated, Roche Diagnostics, Provention Bio, Inc., Consultant; Dexcom, Inc., Janssen Pharmaceuticals, Inc., Medscape. M.Patti: Consultant; MBX Biosciences, AstraZeneca, Hanmi Pharm. Co., Ltd., Other Relationship; Fractyl Health, Inc. E.M.Isganaitis: None. Funding National Institutes of Health (2T32DK007260-46); National Institute of Diabetes and Digestive and Kidney Diseases (5U01DK061230-16)

1638-P: Oxidized Lipids Cause Ceramide Accumulation and Insulin Resistance in Skeletal Muscle

Accumulation of muscle lipids promotes insulin resistance and type 2 diabetes (T2D). Ceramides are important muscle lipids that decrease insulin sensitivity and it was previously shown that accumulation of ceramides in the sarcolemma negatively impacts insulin sensitivity in humans. The mechanisms explaining accumulation of lipids in specific compartments in skeletal muscle are unknown, but one possibility is through circulating oxidized lipids. POVPC, a major circulating oxidized phospholipid, was exposed to rat myotubes (1-50 μM) for 4h and the total cellular ceramide levels in myotubes measured by LC-MS/MS. Total ceramide content increased dose dependently at POVPC doses in the physiological range (5 μM, p <0.05). To determine the mechanism of POVPC induced ceramide accumulation, ceramide was measured in myotubes after treatment with POVPC (25 μM) in the presence of inhibitors of neutral and acid sphingomyelinase (GW4869 and ARC39), ceramide synthase (fumonisin B1) and serine palmitoyltransferase (myriocin). The individually administered inhibitors in the presence of POVPC each showed a decrease (41-55%) in ceramide accumulation. When all of inhibitors were administered together along with POVPC, an almost complete inhibition of ceramide accumulation (95%) was observed indicating that the sphingomyelinase, de novo, and salvage pathways of ceramide synthesis are activated by POVPC. The role of oxidized lipids on insulin sensitivity was examined after treatment of rat myotubes with 1-25 μM POVPC. Increasing doses of POVPC at doses as low as 1 μM significantly decreased insulin sensitivity in vitro (p <0.05). These results reveal circulating oxidized lipids promote ceramide accumulation and insulin resistance in muscle cells and may help explain variability in total and localized muscle ceramide levels between individuals. These data also suggest that therapies designed to lower circulating oxidized lipids could be beneficial for the treatment and prevention of T2D. Disclosure K.Zemski berry: None. B.C.Bergman: Research Support; Eli Lilly and Company. Funding National Institutes of Health (P30DK048520); University of Colorado (25N0350)

Obesity and gestational diabetes independently and collectively induce specific effects on placental structure, inflammation and endocrine function in a cohort of South African women.

Maternal obesity and gestational diabetes mellitus (GDM) are associated with insulin resistance and health risks for mother and offspring. Obesity is also characterized by low-grade inflammation, which in turn, impacts insulin sensitivity. The placenta secretes inflammatory cytokines and hormones that influence maternal glucose and insulin handling. However, little is known about the effect of maternal obesity, GDM and their interaction, on placental morphology, hormones and inflammatory cytokines. In a South African cohort of non-obese and obese pregnant women with and without GDM, this study examined placental morphology using stereology, placental hormone and cytokine expression using real-time PCR, western blotting and immunohistochemistry, and circulating TNFα and IL-6 concentrations using ELISA. Placental expression of endocrine and growth factor genes was not altered by obesity or GDM. However, LEPTIN gene expression was diminished, syncytiotrophoblast TNFα immunostaining elevated and stromal and fetal vessel IL-6 staining reduced in the placenta of obese women in a manner that was partly influenced by GDM status. Placental TNFα protein abundance and maternal circulating TNFα concentrations were reduced in GDM. Both maternal obesity and, to a lesser extent, GDM were accompanied by specific changes in placental morphometry. Maternal blood pressure and weight gain and infant ponderal index were also modified by obesity and/or GDM. Thus, obesity and GDM have specific impacts on placental morphology and endocrine and inflammatory states that may relate to pregnancy outcomes. These findings may contribute to developing placenta-targeted treatments that improve mother and offspring outcomes, which is particularly relevant given increasing rates of obesity and GDM worldwide. KEY POINTS: Rates of maternal obesity and gestational diabetes (GDM) are increasing worldwide, including in low-middle income countries (LMIC). Despite this, much of the work in the field is conducted in higher-income countries. In a well-characterised cohort of South African women, this study shows that obesity and GDM have specific impacts on placental structure, hormone production and inflammatory profile. Moreover, such placental changes were associated with pregnancy and neonatal outcomes in women who were obese and/or with GDM. The identification of specific changes in the placenta may help in the design of diagnostic and therapeutic approaches to improve pregnancy and neonatal outcomes with particular significant benefit in LMICs.

The glycemic, cholesterol, and weight effects of L-carnitine in diabetes: A systematic review and meta-analysis of randomized controlled trials

IntroductionL-carnitine possibly impacts insulin sensitivity and glucose metabolism. However, its therapeutic role in diabetes is poorly understood. MethodsA systematic review and meta-analysis were conducted using PubMed, EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL) from inception through June 30, 2021. Included studies evaluated the use of L-carnitine in diabetes on fasting blood glucose (FBG), hemoglobin A1c (HbA1c), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), weight, or body mass index (BMI). Weighted mean difference (WMD) and 95% confidence intervals (CI) were calculated using the DerSimonian and Laird random-effects model. ResultsSeventeen studies involving 1622 patients were included. Reductions in FBG (WMD = -0.46 mmol/L, 95% CI = -0.68 to -0.23 mmol/L), HbA1c (WMD = -0.5%, 95% CI = -0.8 to -0.1%), TC (WMD = -0.29 mmol/L, 95% CI = -0.42 to -0.16 mmol/L), and LDL-C (WMD = -0.23 mmol/L, 95% CI = -0.39 to -0.07 mmol/L) were significant. Effects on HDL-C, TG, weight, or BMI were insignificant. Doses between 1001 to 2000 mg showed greatest benefit (p < 0.02 for all). Discussion/ConclusionL-carnitine plays a potential role as adjunctive therapy in diabetes. Additional research is necessary for patients with higher baseline HbA1c and type 1 diabetes.

Systemic LSD1 Inhibition Prevents Aberrant Remodeling of Metabolism in Obesity.

The transition from lean to obese states involves systemic metabolic remodeling that impacts insulin sensitivity, lipid partitioning, inflammation, and glycemic control. Here, we have taken a pharmacological approach to test the role of a nutrient-regulated chromatin modifier, lysine-specific demethylase (LSD1), in obesity-associated metabolic reprogramming. We show that systemic administration of an LSD1 inhibitor (GSK-LSD1) reduces food intake and body weight, ameliorates nonalcoholic fatty liver disease (NAFLD), and improves insulin sensitivity and glycemic control in mouse models of obesity. GSK-LSD1 has little effect on systemic metabolism of lean mice, suggesting that LSD1 has a context-dependent role in promoting maladaptive changes in obesity. In analysis of insulin target tissues we identified white adipose tissue as the major site of insulin sensitization by GSK-LSD1, where it reduces adipocyte inflammation and lipolysis. We demonstrate that GSK-LSD1 reverses NAFLD in a non-hepatocyte-autonomous manner, suggesting an indirect mechanism potentially via inhibition of adipocyte lipolysis and subsequent effects on lipid partitioning. Pair-feeding experiments further revealed that effects of GSK-LSD1 on hyperglycemia and NAFLD are not a consequence of reduced food intake and weight loss. These findings suggest that targeting LSD1 could be a strategy for treatment of obesity and its associated complications including type 2 diabetes and NAFLD.

Influence of placental and peripheral malaria exposure in fetal life on cardiometabolic traits in adult offspring

IntroductionFetal malaria exposure may lead to intrauterine growth restriction and increase the risk of developing diabetes and cardiovascular diseases in adulthood. We investigated the extent to which fetal peripheral and...

Abstract P274: Inhibition Of Abnormal Exosome Release Prevents Excessive Aortic Stiffness And Relaxation Dysfunction In Diet-induced Obesity

Interactions between over-nutrition and abnormal exosome release impact insulin sensitivity and the development of cardiovascular disease (CVD). Recent data have shown that exosomes can be released from various cell types, including adipocytes and vascular cells, and that they exist in body fluids and tissues functioning as mediators of cell-cell communication. However, the specific role of exosomes in diet-induced excessive vascular stiffness and hypertension has not been explored. Accordingly, we hypothesized that abnormal release of exosomes contributes to western diet (WD)- induced aortic stiffening and impaired vascular diastolic relaxation. We further posited that GW4869, an antagonist of neutral sphingomyelinase 2 (nSMase2) which promotes exosome production and release, would prevent WD-induced aortic stiffening and impaired vascular relaxation. Six week-old female C57BL/6L mice were fed a mouse chow (CD) or WD containing excess fat (46%) and fructose (17.5%) for 16 weeks with or without GW4849. To this point, 200 μl of 0.3 mg/mL GW4869 in 0.9% normal saline (60 μg/mouse; 2-2.5 μg/g body weight) was injected intraperitoneally every 48 hours for 12 weeks. 16 weeks of WD induced an increase of aortic stiffness as examined by pulse wave velocity (PWV) and impaired the aortic vasodilation responses to acetylcholine (Ach) and sodium nitroprusside (SNP) (10 -9 -10 -4 mol/L). However, GW4869 treatment prevented the WD-induced excessive aortic stiffness, as well as impairment of endothelium dependent/independent vascular relaxation. There were no significant differences in blood pressure between each group examined by tail cuff blood pressure measurement. These findings support the hypothesis that abnormal release of exosomes play an important role in WD-induced excessive aortic stiffness, impaired vascular relaxation and CVD in diet-induced obesity.

Abstract P048: A Model Of Chronic Insufficient Sleep Increases Markers Of Insulin Resistance In Postmenopausal But Not Premenopausal Women

Introduction: Insufficient sleep is widely prevalent among US adults and is a risk factor for type 2 diabetes (T2D). Experimental studies show adverse effects of acute, severe short sleep on insulin sensitivity, but it is unclear whether these reflect risks associated with milder short sleep routinely observed in the general population. To date, no study has evaluated the impact of prolonged mild sleep curtailment on markers of insulin resistance in women or whether these effects differ by menopausal status, known to impact insulin sensitivity. Hypothesis: Glucose and insulin levels, as well as a measure of insulin resistance (HOMA-IR), will increase during 6 wk of sleep restriction (SR) relative to adequate sleep (AS). Adverse effects of prolonged short sleep will be exacerbated in postmenopausal women. Methods: Thirty-four women (age: 38±14 y; BMI: 25.6±3.6 kg/m2; n=10 postmenopausal) with adequate habitual total sleep time (TST) (453±33 min) took part in a randomized crossover study with two 6-wk phases: AS and SR. In AS, participants were asked to maintain stable nightly bed and wake times determined from 2 wk of screening with wrist actigraphy and sleep logs. In SR, bedtime was delayed to reduce TST by approximately 1.5 h/night. Sleep was measured continuously using actigraphy and verified weekly for compliance. At wk 0, 3, 4, and 6 fasting blood samples were collected. Outcomes included glucose and insulin levels as well as HOMA-IR scores, calculated from those values. Linear-mixed models tested interactions of sleep condition with week on outcome measures in the full sample and by menopausal status. Results: Sleep condition impacted the change in TST from baseline (P&lt;0.0001), which was reduced in SR and unchanged in AS (-79±6 vs -4±6min). In the full sample, there was no sleep condition by week interactions for glucose (P=0.67), insulin (P=0.14), or HOMA-IR (P=0.16). Similar results were observed in premenopausal women (all P&gt;0.50). However, in postmenopausal women, there was a significant effect of sleep condition on change in insulin (P=0.046) and HOMA-IR (P=0.039) over the 6 wk. In SR, insulin (slope: 0.26±0.28 μU/mL) and HOMA-IR (slope: 0.07±0.08) increased, while AS resulted in reductions in these outcomes (insulin slope: -0.56±0.29 μU/mL; HOMA-IR slope: -0.16±0.08). Conclusions: We provide the first evidence that chronic short sleep, even if mild, adversely affects insulin sensitivity in postmenopausal women. In contrast, maintenance of AS may improve glycemic regulation. Interestingly, prolonged short sleep did not impact markers of insulin resistance in premenopausal women; further investigation into these life-stage related differences, including underlying mechanisms, is warranted. Results suggest that, in postmenopausal women, a group at heightened risk of poor sleep and T2D, achieving adequate sleep may be an effective strategy to improve cardiometabolic health.

Reduced Insulin Sensitivity in Patients with Myeloid Malignancies and Clonal Hematopoiesis Mutations

Cancer survivors are at increased risk for insulin resistance, which can lead to diabetes mellitus, dyslipidemia, and cardiovascular disease. Whether susceptibility to insulin resistance is due to shared onco-metabolic risk factors, like obesity and older age, or if it originates from malignancy and its treatment is unknown. We investigated metabolic and malignancy-associated risk factors and their effect on insulin sensitivity in patients with treated hematological malignancies. Due to previous glucocorticoid exposure, we hypothesized that patients with lymphoid malignancies would be less insulin sensitive. Nineteen adult patients with treated hematological malignancies but without diabetes mellitus were evaluated with a 2-hour, 75-gram, oral glucose tolerance test (OGTT) and a hyperinsulinemic-euglycemic clamp. Hyperinsulinemic-euglycemic clamps were performed to measure steady-state glucose infusion rate (M-value) as an indicator of whole-body glucose utilization during high-dose insulin stimulation. Decreasing M-values reflect increasing insulin resistance. Patient characteristics were analyzed and compared with OGTT and clamp results. The majority of individuals had myeloid malignancies [MDS/AML (n=7) and CML/MPN (n = 4)]. The remainder were diagnosed with NHL (n=7) and CML lymphoid blast crisis (n=1). All patients were treated before metabolic testing. Sixteen individuals (84%) received cytotoxic chemotherapy and 3 (16%) were administered only tyrosine kinase inhibitors. Median lines of systemic treatment were 2 (range, 1-6), and median time from cancer diagnosis to metabolic testing was 10 months (range, 3-132). Immediately before OGTTs and clamps, 10 (53%) patients were in a complete response, and 9 (47%) had persistent/stable disease. During OGTTs, impaired fasting glucose (plasma glucose 100-125 mg/dL) and impaired glucose tolerance (2-hour plasma glucose 140-199 mg/dL) were respectively observed in 5 (26%) and 6 (32%) patients. M-values were decreased in patients with impaired glucose tolerance. Overweight and obese cancer patients also had lower M-values than individuals with normal body mass indices (BMI) (Table 1). There were otherwise no differences in insulin resistance per age, sex, performance status, ethnicity, or diabetes family history. Differences in insulin resistance were not observed based on exposure to cytotoxic chemotherapy, non-cranial irradiation, numbers of lines of treatment, response, or malignancy duration. Previous glucocorticoid exposure did not impact insulin sensitivity. Surprisingly, patients with myeloid malignancies demonstrated lower M-values (6.92 + 0.54 vs. 12.11 + 1.89; p=0.026) than did those with lymphoid cancers. Acquired mutations involved with myeloid malignancies and clonal hematopoiesis (CH) can increase the risk for atherosclerosis and cardiovascular disease, which are sequelae of insulin resistance. Accordingly, insulin resistance was increased in patients with both a myeloid malignancy and mutations involving either DNMT3A, TET2, ASXL1, or JAK2 compared to myeloid malignancies with unknown/absent CH mutations or lymphoid cancers (6.71 + 0.77 vs. 7.28 + 0.72 vs. 12.11 + 1.89; p=0.031). After adjustment for interaction effect in linear regression modeling, both myeloid malignancy and elevated BMI continued to predict lower insulin sensitivity (Table 2). Pre-diabetes was diagnosed by fasting glucose or OGTT in 26-32% of patients with treated hematological cancers, more than double the prevalence of impaired fasting glucose or impaired glucose tolerance reported by the National Health and Nutrition Examination Survey III. Contrary to our hypothesis, lymphoid cancers and short-term steroids did not contribute to insulin resistance. Instead, myeloid malignancies and CH mutations were associated with reduced insulin sensitivity. Interventions targeting energy balance and obesity will be needed to prevent the harmful sequelae of insulin resistance in long-term cancer survivors. Alternatively, elimination of CH mutations could prove to be a novel treatment of insulin resistance. Disclosures Dholaria: bms: Research Funding; Poseida: Research Funding; Angiocrine: Research Funding; Takeda: Research Funding; J&amp;J: Research Funding.

Label-free CARS microscopy reveals similar triacylglycerol acyl chain length and saturation in myocellular lipid droplets of athletes and individuals with type 2 diabetes

Aims/hypothesisIntramyocellular lipid (IMCL) content associates with development of insulin resistance, albeit not in insulin-sensitive endurance-trained athletes (trained). Qualitative and spatial differences in muscle lipid composition may underlie this so-called athlete’s paradox. Here we studied triacylglycerol (TAG) composition of individual myocellular lipid droplets (LDs) in trained individuals and individuals with type 2 diabetes mellitus.MethodsTrained ( dot{V}{mathrm{O}}_{2max } 71.0 ± 1.6 ml O2 [kg lean body mass (LBM)]−1 min−1), normoglycaemic (fasting glucose 5.1 ± 0.1 mmol/l) individuals and untrained ( dot{V}{mathrm{O}}_{2max } 36.8 ± 1.5 ml O2 [kg LBM]−1 min−1) individuals with type 2 diabetes (fasting glucose 7.4 ± 0.5 mmol/l), with similar IMCL content (3.5 ± 0.7% vs 2.5 ± 0.3%, p = 0.241), but at opposite ends of the insulin sensitivity spectrum (glucose infusion rate 93.8 ± 6.6 vs 25.7 ± 5.3 μmol [kg LBM]−1 min−1 for trained individuals and those with type 2 diabetes, respectively) were included from our database in the present study. We applied in situ label-free broadband coherent anti-Stokes Raman scattering (CARS) microscopy to sections from skeletal muscle biopsies to measure TAG acyl chain length and saturation of myocellular LDs. This approach uniquely permits examination of individual LDs in their native environment, in a fibre-type-specific manner, taking into account LD size and subcellular location.ResultsDespite a significant difference in insulin sensitivity, we observed remarkably similar acyl chain length and saturation in trained and type 2 diabetic individuals (chain length: 18.12 ± 0.61 vs 18.36 ± 0.43 number of carbons; saturation: 0.37 ± 0.05 vs 0.38 ± 0.06 number of C=C bonds). Longer acyl chains or higher saturation (lower C=C number) could be detected in subpopulations of LDs, i.e. large LDs (chain length: 18.11 ± 0.48 vs 18.63 ± 0.57 carbon number) and subsarcolemmal LDs (saturation: 0.34 ± 0.02 vs 0.36 ± 0.04 C=C number), which are more abundant in individuals with type 2 diabetes.Conclusions/interpretationIn contrast to reports of profound differences in the lipid composition of lipids extracted from skeletal muscle from trained and type 2 diabetic individuals, our in situ, LD-specific approach detected only modest differences in TAG composition in LD subpopulations, which were dependent on LD size and subcellular location. If, and to what extent, these modest differences can impact insulin sensitivity remains to be elucidated.Graphical abstract

110-OR: Type 2 Diabetes (T2D)–Associated TCF7L2 Genetic Variants and Indices of Insulin Secretion and Sensitivity in Individuals at Risk for Type 1 Diabetes (T1D)

In individuals with new onset T1D, T2D-associated TCF7L2 genetic variants are associated with lower area-under-the curve (AUC) glucose and higher AUC C-peptide responses to a mixed meal. We aimed to test whether TCF7L2 variants affect glucose metabolism in nondiabetic islet autoantibody-positive (AbPos) individuals. We studied 1065 TrialNet Pathway to Prevention Study participants (AbPos relatives of persons with T1D) with TCF7L2 SNPs who underwent oral glucose tolerance tests (OGTT) (mean age 16.3 yrs, 63% &amp;lt;18 years old, 91.1% non-Hispanic, 47.7% male; T2D-associated TCF7L2 SNP: 48.1% 0 alleles, 43.9% 1 allele, 8% 2 alleles). We assessed the contribution of TCF7L2 SNP variants on Fasting (FIIS) and OGTT Index of Insulin Sensitivity (OIIS), Insulin Secretion (OIISec), and Disposition Index (ODI) with univariate and multivariate analyses. Then we studied the interaction between TCF7L2 SNP and BMI. With Bonferroni correction for multiple comparisons, p-values &amp;lt;0.0086 were considered statistically significant. Insulin sensitivity and secretion indices were significantly associated with age (FIIS, OIIS, OIISec), BMI Z-score (FIIS, OIIS, OIISec, ODI) and Hispanic ethnicity (FIIS, OIIS) but not sex in univariate analyses. TCF7L2 SNP was not significantly associated with these indices in univariate or multivariate analyses adjusting for BMI, age, sex and race-ethnicity. There was a significant interaction between BMI and presence of 2 (vs. 0) TCF7L2 SNP alleles on insulin sensitivity (OIIS) in children (p=0.0079) but not adults (p=0.94). After adjusting for age, ethnicity and sex, the difference did not reach statistical significance (p=0.0135). Restricting to non-obese participants, the results were similar. In sum, in nondiabetic AbPos individuals, the TCF7L2 variant does not appear to impact insulin sensitivity or secretion indices after accounting for BMI, age, sex and race-ethnicity. Disclosure M.J. Redondo: None. M.V. Warnock: None. L.E. Bocchino: None. S. Geyer: None. A. Pugliese: None. A. Steck: None. I. Libman: Consultant; Self; Novo Nordisk A/S. C. Evans-Molina: Consultant; Self; Bristol-Myers Squibb. D.J. Becker: None. J. Sosenko: None. F. Bacha: Research Support; Self; AstraZeneca, Takeda Development Center Americas, Inc. Funding National Institute of Diabetes and Digestive and Kidney Diseases

Physical activity impacts insulin sensitivity post metabolic bariatric surgery in adolescents with severe obesity.

Background/Objectives:We hypothesized that physical activity (PA) improves insulin sensitivity in adolescents with severe obesity beyond that attributable to metabolic bariatric surgery (MBS).Subjects/Methods:StepWatch™ monitors objectively measured PA in 88 participants in the Teen Longitudinal Assessment of Bariatric Surgery (Teen-LABS) study. Primary outcomes included absolute change in fasting insulin, HOMA-IR, and fasting glucose from pre-surgery (baseline) to 6, 12, 24, and 36 months post-MBS. SAS PROC TRAJ generated activity trajectories based on probability and individual participant step count trajectories. Linear regression models were used, adjusted for baseline value, visit, surgical procedure, sex, and percent change in BMI. Additional models adjusted for percent change in iliac waist circumference (IWC) or percent body fat (BF), measured by bio-impedance.Results:Two activity trajectories were identified: more active (MA, n=13) and less active (LA, n=75). MA baseline mean daily step count was >6 000, increasing to > 9 000 at 2 years. LA mean daily step count remained at approximately 4 000. Few participants recorded moderate step activity (cadence >80 steps/minute). Still, fasting insulin and HOMA-IR differed in association with activity trajectory. MA was associated with a greater absolute decrease in fasting insulin (−7.8μU/ml [95% CI: (−11.8, −3.7)], p =<0.001) and a greater decrease in HOMA- IR (−1.9 [95% CI: (−3.0, −0.7)], p = 0.001), when adjusted for percent change in BMI. The significant independent effect of MA remained when adjusted for percent change in IWC or percent BF. Clinically, 100% of MA trajectory participants normalized fasting insulin, HOMA-IR and fasting glucose by 6 months and normalization remained throughout the 36 month follow up. In contrast, 76.3% and 65.8% of LA trajectory participants normalized fasting insulin and HOMA-IR, respectively, by 12 months with 28.6% of both remaining normalized at 36 months.Conclusion:PA is independently associated with improved insulin sensitivity beyond that attributable to MBS in adolescents with severe obesity.

Effect of daily consumption of cranberry beverage on insulin sensitivity and modification of cardiovascular risk factors in adults with obesity: a pilot, randomised, placebo-controlled study.

Cranberries are high in polyphenols, and epidemiological studies have shown that a high-polyphenol diet may reduce risk factors for diabetes and CVD. The present study aimed to determine if short-term cranberry beverage consumption would improve insulin sensitivity and other cardiovascular risk factors. Thirty-five individuals with obesity and with elevated fasting glucose or impaired glucose tolerance participated in a randomised, double-blind, placebo-controlled, parallel-designed pilot trial. Participants consumed 450 ml of low-energy cranberry beverage or placebo daily for 8 weeks. Changes in insulin sensitivity and cardiovascular risk factors including vascular reactivity, blood pressure, RMR, glucose tolerance, lipid profiles and oxidative stress biomarkers were evaluated. Change in insulin sensitivity via hyperinsulinaemic-euglycaemic clamp was not different between the two groups. Levels of 8-isoprostane (biomarker of lipid peroxidation) decreased in the cranberry group but increased in the placebo group (-2·18 v. +20·81 pg/ml; P = 0·02). When stratified by baseline C-reactive protein (CRP) levels, participants with high CRP levels (>4 mg/l) benefited more from cranberry consumption. In this group, significant differences in the mean change from baseline between the cranberry (n 10) and the placebo groups (n 7) in levels of TAG (-13·75 v. +10·32 %; P = 0·04), nitrate (+3·26 v. -6·28 µmol/l; P = 0·02) and 8-isoprostane (+0·32 v. +30·8 pg/ml; P = 0·05) were observed. These findings indicate that 8 weeks of daily cranberry beverage consumption may not impact insulin sensitivity but may be helpful in lowering TAG and changing certain oxidative stress biomarkers in individuals with obesity and a proinflammatory state.

Exercise and Muscle Lipid Content, Composition, and Localization: Influence on Muscle Insulin Sensitivity.

Accumulation of lipid in skeletal muscle is thought to be related to the development of insulin resistance and type 2 diabetes. Initial work in this area focused on accumulation of intramuscular triglyceride; however, bioactive lipids such as diacylglycerols and sphingolipids are now thought to play an important role. Specific species of these lipids appear to be more negative toward insulin sensitivity than others. Adding another layer of complexity, localization of lipids within the cell appears to influence the relationship between these lipids and insulin sensitivity. This article summarizes how accumulation of total lipids, specific lipid species, and localization of lipids influence insulin sensitivity in humans. We then focus on how these aspects of muscle lipids are impacted by acute and chronic aerobic and resistance exercise training. By understanding how exercise alters specific species and localization of lipids, it may be possible to uncover specific lipids that most heavily impact insulin sensitivity.