Reduced Insulin Sensitivity Research Articles

Insulin sensitivity, cardiovascular function and bone health in women with early stage breast cancer before and after cancer treatment.

Cardiovascular disease is a leading cause of death in breast cancer survivors, but the underlying cause is not fully characterised. To determine whether insulin sensitivity, cardiovascular risk markers and body composition were perturbed in women treated with chemotherapy for early stage breast cancer and whether perturbations occurred before or after cancer treatment. Sixteen women with breast cancer and 17 control subjects were studied. Twelve breast cancer patients returned for a second visit following cancer treatment comprising chemotherapy (n=2), or chemotherapy and radiotherapy (n= 10). The Matsuda index to estimate insulin sensitivity, fasting lipids, pulse wave velocity (PWV), reactive hyperaemia index (RHI) and body composition by dual energy X-ray absorptiometry were measured. There were no significant differences in age (53 ± 9 vs 54 ± 11 years; P= 0.82) or body mass index (28 ± 7 vs 28 ± 6; P= 0.97) between patients with breast cancer and controls. Patients with breast cancer had higher triglycerides than controls (1.2 ± 0.1 vs 0.8 ± 0.1 mmol/L; P= 0.03), but there were no significant differences in the Matsuda index, PWV and RHI. Following cancer treatment, there was a lower Matsuda index (6.3 ± 1.2 vs 5.2 ± 1.0; P= 0.01), but this was not associated with a significant change in vascular function. Bone mass fell by 3% from 2.27 ± 0.11 to 2.20 ± 0.10 kg after cancer treatment (P= 0.03). Patients with breast cancer had higher triglycerides before treatment and a reduction in insulin sensitivity and bone mass following cancer treatment. Future larger and longer-term studies should characterise the effect of reduced insulin sensitivity on rates of diabetes, cardiovascular disease, cancer outcomes and fracture. ACTRN12614001055695.

Obesity is the biggest driver of metabolic diseases lets focus on our waists

Obesity is the main determining factor of whole body reduced insulin sensitivity. This association has been demonstrated in multiple adult and pediatric cohorts. A close-fitting relation exists between typical lipid depositions patterns, exactly within the skeletal muscle and liver, as well as the intra-abdominal compartment and whole body insulin sensitivity causing different metabolic disorders. The effect of lipid deposition within insulin responsive tissues such as the liver and skeletal muscle relates to the ability of fatty acid derivate to inhibit elements of the insulin signal transduction pathway. Firming the relation of obesity and reduced insulin sensitivity are the annotations that weight gain reduces insulin sensitivity while weight loss increases it. This displays as the appearance of cardiovascular risk factor clustering with weight gain and its recovery in the face of weight loss. Both obesityand low insulin sensitivity, are independent determinants of the adverse metabolic phenotype characteristic of the metabolic syndrome.

Diabetic Covid-19 severity: Impaired glucose tolerance and pathologic bone loss

Diabetes mellitus (DM), hypertension, and cardiovascular diseases (CVDs) are the leading chronic comorbidities that enhance the severity and mortality of COVID-19 cases. However, SARS-CoV-2 mediated deregulation of diabetes pathophysiology and comorbidity that links the skeletal bone loss remain unclear. We used both streptozocin-induced type 2 diabetes (T2DM) mouse and hACE2 transgenic mouse to enable SARS-CoV-2-receptor binding domain (RBD) mediated abnormal glucose metabolism and bone loss phenotype in mice. The data demonstrate that SARS-CoV-2-RBD treatment in pre-existing diabetes conditions in hACE2 (T2DM + RBD) mice results in the aggravated osteoblast inflammation and downregulation of Glucose transporter 4 (Glut4) expression via upregulation of miR-294–3p expression. The data also found increased fasting blood glucose and reduced insulin sensitivity in the T2DM + RBD condition compared to the T2DM condition. Femoral trabecular bone mass loss and bone mechanical quality were further reduced in T2DM + RBD mice. Mechanistically, silencing of miR-294 function improved Glut4 expression, glucose metabolism, and bone formation in T2DM + RBD + anti-miR-294 mice. These data uncover the previously undefined role of SARS-CoV-2-RBD treatment mediated complex pathological symptoms of diabetic COVID-19 mice with abnormal bone metabolism via a miRNA-294/Glut4 axis. Therefore, this work would provide a better understanding of the interplay between diabetes and SARS-CoV-2 infection.

Three months of melatonin treatment reduces insulin sensitivity in patients with type 2 diabetes-Arandomized placebo-controlled crossover trial.

The use of the sleep‐promoting hormone melatonin is rapidly increasing as an assumed safe sleep aid. During the last decade, accumulating observations suggest that melatonin affects glucose homeostasis, but the precise role remains to be defined. We investigated the metabolic effects of long‐term melatonin treatment in patients with type 2 diabetes including determinations of insulin sensitivity and glucose‐stimulated insulin secretion. We used a double‐blinded, randomized, placebo‐controlled, crossover design. Seventeen male participants with type 2 diabetes completed (1) 3 months of daily melatonin treatment (10 mg) 1 h before bedtime (M) and (2) 3 months of placebo treatment 1 h before bedtime (P). At the end of each treatment period, insulin secretion was assessed by an intravenous glucose tolerance test (0.3 g/kg) (IVGTT) and insulin sensitivity was assessed by a hyperinsulinemic‐euglycemic clamp (insulin infusion rate 1.5 mU/kg/min) (primary endpoints). Insulin sensitivity decreased after melatonin (3.6 [2.9–4.4] vs. 4.1 [3.2–5.2] mg/(kg × min), p = .016). During the IVGTT, the second‐phase insulin response was increased after melatonin (p = .03). In conclusion, melatonin treatment of male patients with type 2 diabetes for 3 months decreased insulin sensitivity by 12%. Clinical use of melatonin treatment in dosages of 10 mg should be reserved for conditions where the benefits will outweigh the potential negative impact on insulin sensitivity.

Vildagliptin alleviates liver fibrosis in NASH diabetic rats via modulation of insulin resistance, oxidative stress, and inflammatory cascades

AimsThis study investigates the therapeutic potential of Vilda in a NASH model with liver fibrosis and elucidates the underlying molecular mechanisms. Main methodsTo induce NASH, male Sprague-Dawley rats were fed a high-fat diet for 24 weeks with a single dose of STZ (40 mg/kg, IP). Vilda was orally administered at two doses (10 and 20 mg/kg) for 20 weeks. Key findingsThe induction of NASH was validated by abnormalities in hepatotoxicity indices, lipid profile, oxidative stress markers, and pathologically by marked fat deposition in hepatic tissues together with severe inflammatory cell infiltration. Moreover, NASH-affected rats demonstrated reduced insulin sensitivity manifested as elevated fasting blood glucose levels and disrupted homeostasis model assessment for insulin resistance. Vilda, at both doses, effectively abrogated all these pathological features of NASH. Mechanistically, these hepatoprotective properties of Vilda can be attributed to its antioxidant effects, anti-inflammatory effects (by inhibiting the TNF-α, NF-κB, JNK, and JAK/STAT pathways), and insulin-sensitizing effect (by upregulating the IRS-1/PI3K/Akt pathway). Besides, Vilda successfully counteracted NASH-associated liver fibrosis by downregulating the TGF-β1 pathway. SignificanceThe hepatoprotective and antifibrotic effects of Vilda were mostly dose-dependent. Collectively, this study offered a promising therapeutic avenue for Vilda as a novel strategy for counteracting the pathological progression of NASH and associated liver fibrosis.

745-P: Short-Acting Exenatide Added Three Times Daily to Insulin Therapy Improves Insulin Sensitivity in Type 1 Diabetes

Average life expectancy in type 1 diabetes is reduced by more than a decade due to cardiovascular (CV) disease. Reduced insulin sensitivity as assessed by low values of estimated glucose disposal rate (eGDR) has been observed to correlate with increased risk of CV events. How short-acting glucagon-like peptide 1 receptor agonists (GLP-1RA) influence eGDR in type 1 diabetes remains unknown. We analyzed eGDR post-hoc in a phase 2, double-blind, randomized (1:1) , clinical trial (NCT03017352) that evaluated the short-acting GLP-1RA exenatide μg added three times daily to insulin therapy as compared with placebo over 26 weeks of treatment in 1individuals with type 1 diabetes (76/32 men/women, age 50 (14) years (mean (standard deviation)) , diabetes duration 21 (12) years, BMI 28 (4) kg/m2, glycated hemoglobin A1c 8.2 (0.7) % / 66 (7) mmol/mol) . Exenatide significantly increased eGDR by 0.36 mg/kg/min (95 % confidence interval 0.03; 0.69, P = 0.032) (Table 1) as compared with placebo after 26 weeks’ treatment. Short-acting exenatide apparently improved insulin sensitivity in patients with long-standing type 1 diabetes and inadequate glycemic control, alluding to potential CV benefits of this GLP-1RA in type 1 diabetes. Disclosure N.Johansen: Employee; Novo Nordisk A/S. T.F.Dejgaard: Advisory Panel; Novo Nordisk, Research Support; Novo Nordisk, Speaker's Bureau; AstraZeneca, Boehringer Ingelheim International GmbH, Novo Nordisk. A.Lund: Speaker's Bureau; Novo Nordisk A/S. T.Vilsbøll: Consultant; AstraZeneca, Bristol-Myers Squibb Company, Eli Lilly and Company, Gilead Sciences, Inc., GlaxoSmithKline plc., Merck Sharp & Dohme Corp., Mundipharma, Novo Nordisk, Sun Pharmaceutical Industries Ltd. H.U.Andersen: Advisory Panel; Abbott Diabetes, Stock/Shareholder; Novo Nordisk A/S. F.K.Knop: Advisory Panel; Boehringer Ingelheim International GmbH, Eli Lilly and Company, Merck Sharp & Dohme Corp., Novo Nordisk, Sanofi, ShouTi, Zucara Therapeutics, Consultant; AstraZeneca, Eli Lilly and Company, Novo Nordisk, Pharmacosmos A/S, Sanofi, ShouTi, Zealand Pharma A/S, Zucara Therapeutics, Research Support; AstraZeneca, Novo Nordisk, Sanofi, Zealand Pharma A/S, Speaker's Bureau; AstraZeneca, Bayer AG, Boehringer Ingelheim International GmbH, Eli Lilly and Company, Novo Nordisk, Sanofi, Stock/Shareholder; Antag Therapeutics. Funding Partly funded by AstraZeneca

137-OR: A Genetic Approach to Detangling the Heterogeneity of Fasting Insulin Levels

Fasting insulin (FI) is a heterogeneous trait with high variability between individuals and populations. Increased FI is associated with an increased risk of type 2 diabetes (T2D) and its complications, including coronary artery disease (CAD) and hypertension (HTN) . We hypothesize that we could use a genetic approach to cluster FI-associated variants, characterize the clusters in terms of insulin processes within the Mexican American Cardiovascular Disease Study (MACAD; N=821) , and test for association of polygenic scores (PS) created from these clusters with T2D, CAD and HTN in three cohorts: Mass General Brigham Biobank (MGBB; N=18,127) , Aspirin in Reducing Events in the Elderly (ASPREE; N=13,349) , and Framingham Heart Study (FHS; N=7,145) . We identified six clusters using a soft clustering approach with 446 FI-increasing genetic alleles and 27 FI-related traits. Associations in two of the clusters, allowed us to characterize them and show their impact on T2D and T2D-associated complications. The first cluster had alleles associated with increased subcutaneous and visceral adiposity and was characterized by reduced insulin sensitivity (from euglycemic clamp; P=0.02) , increased insulin secretion (from oral glucose tolerance test [OGTT]; P=0.04) , and increased insulin clearance (from euglycemic clamp; P=0.02) in MACAD. This cluster’s PS was associated with HTN (MGBB Odds ratio (OR) = 1.04, P=0.013) , T2D (MGBB OR = 1.04, P =0.001) and CAD (MGB OR=1.07, P =0.008; ASPREE OR=1.04, P =0.036) The second cluster had alleles associated with a lipodystrophy phenotype and was characterized by increased insulin secretion (from OGTT P =0.019) in MACAD. We observed associations of the PS with T2D (MGBB OR= 1.13, P =2.3x10-10) and HTN (MGBB OR = 1.06, P =0.001) which were replicated in ASPREE and FHS. Our results suggest the presence of two different FI-associated genetic domains and elucidate the deleterious mechanisms by which increased FI is associated with T2D and T2D complications. Disclosure M.Sevilla: None. M.O.Goodarzi: None. D.A.Dicorpo: None. J.I.Rotter: None. J.B.Meigs: Consultant; Quest Diagnostics. M.Udler: None. A.Manning: None. Funding UM1DK078616

228-OR: Differential Expression of miRNA in Human Subcutaneous and Visceral Adipose Tissue Is Related to Insulin Resistance

Introduction: Obesity is related to insulin resistance (IR) but not all obese individuals are IR. Differences in regional fat distribution and function contribute to the metabolic heterogeneity of obesity. miRNA is known to regulate mRNA and may play a role in mediating IR by modifying adipose tissue function. We tested the hypothesis that miRNA in human visceral (VAT) and subcutaneous (SAT) fat would be differentially expressed in individuals who were classified as insulin sensitive (IS) or IR. Methods: 12 participants, classified as IR or IS (top 40 percentile) via steady-state plasma glucose (SSPG) test, were recruited from the Stanford Bariatric Surgery Clinic. Tissue samples (SAT and VAT) were harvested from the greater momentum during bariatric surgery. Total RNA was extracted with QIAGEN RNeasy® Lipid Tissue Mini Kit. The miRNA experiment used QuantStudio™ 12K Flex OpenArray® microRNA Starter Kit with modifications by adding Ath-miR-159a spike-in, and use of SuperScript VILO cDNA Synthesis Kit. Data analysis done via Applied Biosystems™ Relative Quantitation Analysis. miRNA comparisons with fold-change <0.5 or >2 and p<0.were considered statistically significant. Known target genes of significant miRNA were quantified via RT-PCR from tissue samples. Results: Differential expression in VAT vs. SAT showed one upregulated (miR-885-5p) and 12 downregulated miRNAs. In SAT, for IR vs. IS individuals showed 12 upregulated miRNA, while in VAT, IR vs. IS included one upregulated (miR-30c) and downregulated miRNA. Conclusion: In VAT relative to SAT, miR-885-5p was a significant predictor of fatty liver and majority of downregulated miRNA (miR-335, 196b, 497, 22, 106b, 340) reduced lipogenesis and increased insulin signaling. In IR vs. IS of SAT, majority of miRNA reduced insulin sensitivity (miR-146b, 29c, 502-3p) . For IR vs. IS of VAT, miR-30c promoted adipocyte differentiation and majority of downregulated miRNA increased insulin sensitivity (miR-106b, 24, 143, 340) . Disclosure N.Saini: None. A.Deng: None. H.Chen: None. Y.Xu: None. P.S.Tsao: None. T.Mclaughlin: Board Member; January, Inc., Research Support; Merck & Co., Inc., Novo Nordisk, Stock/Shareholder; Eiger BioPharmaceuticals.

198-LB: The Loss of the Lysine Acetyltransferase KAT8 in Adipocytes Confers Lipodystrophy and Metabolic Dysfunction in Male and Female Mice

KAT8, also known as MOF or MYST1, is a lysine acetyltransferase with both histone and non-histone substrates. While KAT8 is the major H4K16 acetyltransferase in Drosophila and mammals and is essential for embryonic development, its role in specific cell types is not well understood. Moreover, studies within the past decade have demonstrated lineage-, differentiation state-, or stress-dependent roles of KAT8. Our recent efforts have shown that KAT8 is necessary for in vitro adipogenesis prior to or during the proliferative phase. Notably, several, independent genetic studies reveal that single nucleotide polymorphisms (SNPs) within or near the KAT8 gene are associated with body mass index and/or waist circumference. To investigate the role of KAT8 in differentiated adipocytes and to understand the contribution of KAT8-deficient adipocytes to whole-body glucose and lipid metabolism, we generated both congenital and doxycycline-inducible adipocyte-specific knockout mice, in which Kat8 gene deletion occurs only in adiponectin-expressing cells. Adult mice lacking adipocyte KAT8 exhibited significant fat mass loss with no change in lean mass. While the size of inguinal and brown adipose tissue was significantly reduced in both sexes fed either chow or high-fat, high-sucrose (HFHS) diet, male mice also had decreased gonadal, retroperitoneal, and mesenteric depots. Histological assessments revealed substantial remodeling within adipose tissue depots, and these mice demonstrated reduced insulin sensitivity and increased lipid accumulation in the liver when fed HFHS diet. Although further investigation is necessary to identify KAT8 targets that confer lipodystrophy, these studies are the first to show the impact of the loss of adipocyte KAT8 in vivo. Disclosure A. J. Richard: n/a. T. M. Mendoza: None. J. M. Stephens: None. Funding National Institutes of Health COBRE P&F grant (P30 GM118430)

1360-P: Calorie Restriction Enhanced Glycogen Metabolism to Compensate for Lipid Insufficiency

Backgrounds: It's well known that calorie restriction (CR) brings striking benefits in metabolic improvement with complex and unclear mechanism. In this study, we aimed to investigate the specific manifestation and possible mechanisms of metabolism in CR mice. Methods: B6 mice were randomly assigned to three groups: (1) chow diet (control) , (2) chow diet with 40% calorie restriction (CR) , (3) high-fat diet (HFD) . The metabolism status and related examination were performed after 12 weeks of feeding. Results: In this study, we found that CR increased fasting blood glucose and plasma insulin, as well as reduced insulin sensitivity reflected by insulin tolerance test. Comparing to the control mice, the decrease of phosphorylation levels of IRS-1 including serine307 and tyrosine632 residues, and AKT (threonine308) after insulin rejection further confirmed that CR induced insulin resistance. Different from insulin resistance induced by HFD, CR improved glucose tolerance and reduced gluconeogenesis. Meanwhile, CR led to absolute lipid reduction, manifested in decreased plasma lipid, liver lipid deposition and fat mass. In contrast, liver glycogen increased dramatically. Fasting glycogen was twice as much as that of HFD group and 20 times as that of control group. Furthermore, the CR increased p-PYGL, p-GSK3β and decreased p-GS notably indicating active glycogen synthesis and decomposition. Subsequently, we found that CR increased plasma corticosterone and decreased plasma c-reactive protein (CRP) compared with control and HFD groups, while plasma corticosterone and CRP in HFD were higher than those in control group. Additionally, CR lowered levels of orexigenic neuropeptides and elevated levels of anorexigenic neuropeptides. Conclusions: Our study suggested that CR induced lipid insufficiency and stress from starvation, resulting in physiological insulin resistance and enhanced glycogen metabolism, including increased glycogen synthesis, glycogenolysis and glycogen content. Disclosure L.Hu: None. X.Xia: None. Y.Gu: None. J.Yin: None. Funding National Natural Science Foundation of China (No. 82070885) ,Shanghai Municipal Education Commission—Gaofeng Clinical Medicine Grant Support (No. 20172025)

Effects of Bromocriptine on Glucose and Insulin Dynamics in Normal and Insulin Dysregulated Horses.

The objectives of the study were to study the effects of the synthetic ergot alkaloid (EA), bromocriptine, on glucose and lipid metabolism in insulin dysregulated (ID, n = 7) and non-ID (n = 8) mares. Horses were individually housed and fed timothy grass hay and two daily concentrate meals so that the total diet provided 120% of daily DE requirements for maintenance. All horses were given intramuscular bromocriptine injections (0.1 mg/kg BW) every 3 days for 14 days. Before and after 14 days of treatment horses underwent a combined glucose-insulin tolerance test (CGIT) to assess insulin sensitivity and a feed challenge (1 g starch/kg BW from whole oats) to evaluate postprandial glycemic and insulinemic responses. ID horses had higher basal plasma concentrations of insulin (P = 0.01) and triglycerides (P = 0.02), and lower concentrations of adiponectin (P = 0.05) compared with non-ID horses. The CGIT response curve showed that ID horses had slower glucose clearance rates (P = 0.02) resulting in a longer time in positive phase (P = 0.03) and had higher insulin concentrations at 75 min (P = 0.0002) compared with non-ID horses. Glucose (P = 0.02) and insulin (P = 0.04) responses to the feeding challenge were lower in non-ID compared to ID horses. Regardless of insulin status, bromocriptine administration increased hay intake (P = 0.03) and decreased grain (P < 0.0001) and total DE (P = 0.0002) intake. Bromocriptine treatment decreased plasma prolactin (P = 0.0002) and cholesterol (P = 0.10) and increased (P = 0.02) adiponectin concentrations in all horses. Moreover, in both groups of horses, bromocriptine decreased glucose clearance rates (P = 0.02), increased time in positive phase (P = 0.04) of the CGIT and increased insulin concentrations at 75 min (P = 0.001). The postprandial glycemic (P = 0.01) and insulinemic (P = 0.001) response following the oats meal was lower after bromocriptine treatment in all horses. In conclusion, in contrast to data in humans and rodents, bromocriptine treatment reduced insulin sensitivity in all horses, regardless of their insulin status. These results indicate that the physiological effects of EA might be different in horses compared to other species. Moreover, because bromocriptine shares a high degree of homology with natural EA, further investigation is warranted in horses grazing endophyte-infected grasses.

Reduced insulin signaling and high glucagon in early insulin resistance impaired fast-fed regulation of renal gluconeogenesis via insulin receptor substrate.

Gluconeogenesis is one of the key processes through which the kidney contributes to glucose homeostasis. Urinary exosomes (uE) have been used to study renal gene regulation noninvasively in humans and rodents. Recently, we demonstrated fast-fed regulation of phosphoenolpyruvate carboxykinase (PEPCK), the rate-limiting enzyme for gluconeogenesis, in human uE. The regulation was impaired in subjects with early insulin resistance. Here, we studied primary human proximal tubule cells (hPT) and human uE to elucidate a potential link between insulin resistance and fast-fed regulation of renal PEPCK. We demonstrate that fasted hPTs had higher PEPCK and insulin receptor substrate-2 (IRS2) mRNA and protein levels, relative to fed cells. The fast-fed regulation was, however, attenuated in insulin receptor knockdown (IRKO) hPTs. The IRKO was confirmed by the blunted insulin-induced response on PEPCK, PGC1α, p-IR, and p-AKT expression in IRKO cells. Exosomes secreted by the wild-type or IRKO hPT showed similar regulation to the respective hPT. Similarly, in human uE, the relative abundance of IRS-2 mRNA (to IRS1) was higher in the fasted state relative to the fed condition. However, the fast-fed difference was absent in subjects with early insulin resistance. These subjects had higher circulating glucagon levels relative to subjects with optimal insulin sensitivity. Furthermore, in hPT cells, glucagon significantly induced PEPCK and IRS2 gene, and gluconeogenesis. IR knockdown in hPT cells further increased the gene expression levels. Together the data suggest that reduced insulin sensitivity and high glucagon in early insulin resistance may impair renal gluconeogenesis via IRS2 regulation.

Cesarean Delivery and Insulin Sensitivity in the Older Adult: The Microbiome and Insulin Longitudinal Evaluation Study.

The present study was designed to evaluate if mode of delivery at birth is associated with body mass index (BMI) and glucose homeostasis traits in later life, controlling for possible confounders, including maternal history of diabetes. Data were obtained through a racially diverse, prospective cohort study of nondiabetic, older adults, the Microbiome and Insulin Longitudinal Evaluation Study (MILES). We used generalized linear models to estimate the association between mode of delivery and glycemic status, BMI (kg/m2), waist circumference (cm), fasting glucose, fasting insulin, insulin secretion, insulin sensitivity, and insulin clearance. Further, we estimated the direct and indirect effects of cesarean delivery on glucose and insulin-related traits, as mediated by BMI status. Relative to vaginal delivery, cesarean delivery was associated with a significantly higher BMI (adjusted beta [aβ] 3.53 kg/m2; 95% CI 0.15, 6.91) and fasting glucose (aβ 5.12; 95% CI 0.01, 10.23), a 14% decrease in insulin sensitivity (aβ –0.14; 95% CI –0.28, –0.01), and a 58% increased risk (adjusted relative risk [aRR] 1.58; 95% CI 1.08, 2.31) for prediabetes/diabetes. Associations were mediated in part by BMI, with the strongest evidence observed for glycemic status (proportion mediated 22.6%; P = .03), fasting insulin (proportion mediated 58.0%; P = .05), and insulin sensitivity index (proportion mediated 45.9%; P = .05). Independent of mediation, a significant direct effect of cesarean delivery on glycemic status was observed (aRR 1.88; 95% CI 1.16, 2.60). Cesarean delivery may lead to reduced insulin sensitivity and, ultimately, increased risk for developing prediabetes and diabetes.

Renal gluconeogenesis induction by glucagon and insulin receptor deletion in humans

Gluconeogenesis is one of the key processes through which the kidney contributes to glucose homeostasis. Recently, we provided evidence to suggest that early insulin resistance may impair fast‐fed regulation of Phosphoenolpyruvate Carboxykinase (PEPCK), rate‐limiting enzyme for gluconeogenesis in humans. To confirm this and to elucidate a link between insulin resistance and fast‐fed regulation of PEPCK in the kidneys, we studied primary proximal tubule cells (hPT) and urinary extracellular vesicles (uEVs) from humans. We demonstrate that fasted hPTs had higher PEPCK and insulin receptor substrate‐2 (IRS2) mRNA levels than fed cells. The fast‐fed regulation was, however, attenuated in insulin receptor knockdown hPTs (IRKO). The insulin receptor knockdown was confirmed by a blunted insulin‐induced suppression in PEPCK and PGC1α mRNA and p‐IR and p‐AKT protein expression in IRKO cells. Exosomes secreted by the wild‐type or IRKO hPT showed similar regulation as observed in the respective hPT. Similarly, in human uE, the relative abundance of IRS‐2 mRNA (to IRS1) was higher in the fasted state relative to the fed condition. However, the fast‐fed difference was absent in subjects with early insulin resistance. These subjects had higher circulating glucagon levels relative to subjects with optimal insulin sensitivity. Furthermore, in hPT cells, glucagon significantly induced PEPCK mRNA, IRS2 mRNA, and gluconeogenesis. Insulin receptor deletion further increased their levels. Together the data suggest that reduced insulin sensitivity and high glucagon in early insulin resistance may impair renal gluconeogenesis via IRS2 regulation. Funding from ICMR‐CARE and SGPGI intramural to ST and CSIR to RS.

Mitochondrial Dysfunction Dictates Energy Metabolism Reprogramming in Pulmonary Arterial Hypertension

IntroductionPulmonary arterial hypertension (PAH) is a progressive fatal disease with a complex pathogenic mechanism. Recent studies report that nearly 60% of patients with PAH have metabolic syndrome (MS). Unrecognized glucose intolerance and insulin resistance were also shown to be common in PAH, raising the possibility that metabolic disease predisposes to PAH. Nevertheless, the mechanistic link between the PAH and metabolic disorders remains unexplored. Mitochondrial dysfunction (MD) is one of the primary pathogenic events tightly associated with PAH and MS/ type 2 diabetes pathobiology and could play a causative role in severe metabolic perturbations.HypothesisWe hypothesized that dysfunctional mitochondria are sufficient to initiate metabolic rearrangements associated with PAH and classical metabolic disorders.MethodsIn this study, we used the recently established rat model reproducing a human mutation in the NFU1 protein, which is responsible for mitochondrial homeostasis. NFU1G206Crats develop a severe MD and spontaneously develop PAH characterized by increased right ventricle (RV) systolic pressure, RV hypertrophy, and obliterative disease of the small pulmonary arteries. An intraperitoneal glucose tolerance test (IPGTT) was used to assess the ability of NFU1G206Crats to metabolize glucose. Plasma insulin levels were measured to control insulin sensitivity. Pulmonary arterial smooth muscle cells (PASMCs) isolated from WT and NFU1G206C rats were used for measuring fatty acid oxidation (FAO) by Seahorse palmitate‐BSA oxidation assay, mitochondria isolations, and western blot analysis.ResultsAfter 5 hours of fasting, WT and NFU1G206C rats had the same baseline glucose levels (glucose (mg/dL) is 89.5±2.0 vs. 92.0±6.2; p=0.47 in WT (N=5) vs. NFU1G206C(N=6)). However, 15 min after glucose administration (2 g/kg), NFU1G206Cshowed significantly higher levels of blood glucose, which reached the peak by 30 min (193.4±32.3 vs. 340.8±50.1; p&lt;0.05 in WT vs. NFU1G206C) and remained high even after 120 min, when the glucose level of WT rats reached the baseline (96.1±11.1 vs. 155.9±15.9; p&lt;0.02 in WT vs. NFU1G206C). MD was also sufficient to induce a significantly delayed insulin response in NFU1G206Ccompared to WT, suggesting the reduced insulin sensitivity in rats with MD. We also discovered an upregulated expression of free fatty acid (FFA) transporters, CD36 and CPT1, in NFU1G206C PASMC, which corresponded to the increased levels of basal FAO in the mutant cells. This discovery was confirmed by mitochondrial proteome analysis, revealing a significantly upregulated FA metabolism and dysregulated FA synthesis in NFU1G206C PASMC. NFU1G206C PASMC also had an increased membrane translocation of PKCα, one of the diacylglycerol‐dependent PKCs activated by FFAs and involved in reduced insulin sensitivity.ConclusionWe conclude that the MD secondary to the NFU1 insufficiency induces significant metabolic derangements, such as increased flux of fatty acids, glucose intolerance, and insulin insensitivity associated with classic metabolic disorders and recently implemented in the pathogenesis of PAH. The severe metabolic reprogramming revealed in PASMC correlates with progressive pulmonary vascular disease in NFU1G206Crats.

Insulin action and resistance are dependent on a GSK3\u03b2-FBXW7-ERR\u03b1 transcriptional axis

Insulin resistance, a harbinger of the metabolic syndrome, is a state of compromised hormonal response resulting from the dysregulation of a wide range of insulin-controlled cellular processes. However, how insulin affects cellular energy metabolism via long-term transcriptional regulation and whether boosting mitochondrial function alleviates insulin resistance remains to be elucidated. Herein we reveal that insulin directly enhances the activity of the nuclear receptor ERRα via a GSK3β/FBXW7 signaling axis. Liver-specific deletion of GSK3β or FBXW7 and mice harboring mutations of ERRα phosphosites (ERRα3SA) co-targeted by GSK3β/FBXW7 result in accumulated ERRα proteins that no longer respond to fluctuating insulin levels. ERRα3SA mice display reprogrammed liver and muscle transcriptomes, resulting in compromised energy homeostasis and reduced insulin sensitivity despite improved mitochondrial function. This crossroad of insulin signaling and transcriptional control by a nuclear receptor offers a framework to better understand the complex cellular processes contributing to the development of insulin resistance.

Glucocorticoid-induced hyperglycaemia and diabetes: Call for action.

Glucocorticoid-induced hyperglycaemia and diabetes: Call for action.

IGF-1 ameliorates streptozotocin-induced pancreatic β cell dysfunction and apoptosis via activating IRS1/PI3K/Akt/FOXO1 pathway.

Type 2 diabetes mellitus (T2DM) is an endocrine disorder with pancreatic β cell dysfunction and/or reduced insulin sensitivity. IGF-1 is critically involved in pancreatic β cell growth, differentiation, and insulin secretion. Insulin-mediated IRS1/PI3K/Akt/FOXO1 signaling has been proved to be closely associated with pancreatic β cell function, hepatic glucose metabolism, and the development of T2DM. This present work was designed to demonstrate the protective role of IGF-1 against pancreatic β cell dysfunction and to probe into the underlying mechanisms. Herein, cell viability, cell apoptosis, insulin secretion, oxidative stress, and glycolysis in STZ-treated INS-1 cells were measured, so as to determine the biological function of IGF-1 against pancreatic β cell dysfunction in T2DM. Additionally, whether IGF-1 could activate IRS1/PI3K/Akt/FOXO1 signaling pathway to manipulate the progression of T2DM was also investigated. It was discovered that IGF-1 treatment enhanced the viability and suppressed the apoptosis of STZ-treated INS-1 cells. Besides, IGF-1 treatment augmented insulin secretion of INS-1 cells in response to STZ. Moreover, IGF-1 exerted protective role against oxidative damage and displayed inhibitory effect on glycolysis in STZ-treated INS-1 cells. Mechanistically, IGF-1 treatment markedly boosted the activation of IRS1/PI3K/Akt/FOXO1 pathway. Furthermore, treatment with AG1024 (an inhibitor of IGF-1R) partially abolished the actions of IGF-1 on cell viability, cell apoptosis, insulin secretion, oxidative stress, and glycolysis in STZ-treated INS-1 cells. To conclude, IGF-1 could improve the viability and inhibit the apoptosis of STZ-treated pancreatic β cells, induce insulin secretion, alleviate oxidative damage, as well as arrest glycolysis by activating IRS1/PI3K/Akt/FOXO1 pathway.

Estradiol replacement improves high-fat diet-induced insulin resistance in ovariectomized rats.

The role of 17β‐estradiol (E2) in high‐fat diet (HFD)‐induced alteration of the protein kinase B (Akt) signaling pathway in ovariectomized (OVX) rats is unclear. Therefore, we examined whether chronic estrogen replacement restores HFD‐induced impairment in insulin sensitivity by its effects concomitant with alterations in the Akt isoform 2 (Akt2) and Akt substrate of 160 kDa (AS160) phosphorylation in muscles of OVX rats. Nine‐week‐old female Wistar rats underwent ovariectomy under anesthesia; after 4 weeks, subcutaneous implantation of either E2 or placebo (PL) pellets was performed, and HFD feeding was initiated. Intravenous glucose tolerance tests were performed to assess insulin sensitivity. Following insulin injection into rats’ portal vein, the liver and gastrocnemius muscle were dissected for insulin signaling analysis. We observed that HFD increased energy intake and body weight in the PL group; however, it was temporarily decreased in the E2 group. Adipose tissue accumulation was larger in HFD‐fed rats than in normal chow diet (NCD)‐fed rats in the PL group; however, this difference was not observed in the E2 group. HFD reduced insulin sensitivity in the PL group only. In vivo insulin stimulation increased Akt2 phosphorylation in the muscles of NCD‐fed rats in both groups. In contrast, HFD affected insulin‐stimulated phosphorylation of Akt2 and AS160 in the muscles of rats in the PL group but not in the E2 group. Our data suggest that E2 replacement improves HFD‐induced insulin resistance, and this effect is accompanied by the alterations in the Akt2 and AS160 phosphorylation in insulin‐stimulated muscles of OVX rats.

Supplementation of Rumen-Protected Glucose Increased the Risk of Disturbance of Hepatic Metabolism in Early Postpartum Holstein Cows.

The dual stress of reduced feed intake and increased milk yield in dairy cows early postpartum results in a negative energy balance. Rumen-protected glucose (RPG) has been reported to replenish energy, increase milk yield, and improve gut health. However, early postpartum cows often develop an insulin resistance, implying that RPG may not be well utilized and increased milk production may increase the liver’s fat oxidization burden. This study aimed to investigate the effects of RPG on the hepatic oxidative/antioxidative status and protein profile. Starting 7 d before expected calving, six pairs of cows were supplemented with rumen-protected glucose (RPG, n = 6) or with an equal amount of rumen-protecting coating fat (CON, n = 6). Liver samples were obtained from 10 cows 14 d after calving (d 14). Concentration of malondialdehyde and activity of glutathione peroxidase were increased and the activities of catalase and superoxide dismutase tended to increase in the livers of the RPG cows compared to the CON cows. The revised quantitative insulin sensitivity check index (RQUICKI) was decreased by RPG, but triacylglycerol concentration in liver was increased by RPG supplementation. The overall profiles of hepatic proteins were similar between CON and RPG. A partial least square regression was conducted to identify the proteins associated with liver lipidosis, oxidative stress, and antioxidative capacity. The top twenty proteins, according to their variable importance value, were selected for metabolic pathway enrichment analysis. Eighteen enriched KEGG pathways were identified, including metabolism, the citrate cycle, propanoate metabolism, the peroxisome, and type II diabetes mellitus. Our study showed that RPG supplementation reduced insulin sensitivity but increased the liver triglyceride concentration and the oxidative stress in early postpartum cows. Liver proteins related to lipidosis, oxidative stress, and antioxidative capacity, were positively associated with the glutamine metabolism, citric acid cycle, peroxisome, and type II diabetes pathways, which may indicate an increased risk of liver metabolic disorders caused by RPG supplementation in early postpartum cows.