Basal Glucose Production Research Articles

Inhibition of basal and glucagon-induced hepatic glucose production by 991 and other pharmacological AMPK activators.

Pharmacological AMPK activation represents an attractive approach for the treatment of type 2 diabetes (T2D). AMPK activation increases skeletal muscle glucose uptake, but there is controversy as to whether AMPK activation also inhibits hepatic glucose production (HGP) and pharmacological AMPK activators can have off-target effects that contribute to their anti-diabetic properties. The main aim was to investigate the effects of 991 and other direct AMPK activators on HGP and determine whether the observed effects were AMPK-dependent. In incubated hepatocytes, 991 substantially decreased gluconeogenesis from lactate, pyruvate and glycerol, but not from other substrates. Hepatocytes from AMPKβ1-/- mice had substantially reduced liver AMPK activity, yet the inhibition of glucose production by 991 persisted. Also, the glucose-lowering effect of 991 was still seen in AMPKβ1-/- mice subjected to an intraperitoneal pyruvate tolerance test. The AMPK-independent mechanism by which 991 treatment decreased gluconeogenesis could be explained by inhibition of mitochondrial pyruvate uptake and inhibition of mitochondrial sn-glycerol-3-phosphate dehydrogenase-2. However, 991 and new-generation direct small-molecule AMPK activators antagonized glucagon-induced gluconeogenesis in an AMPK-dependent manner. Our studies support the notion that direct pharmacological activation of hepatic AMPK as well as inhibition of pyruvate uptake could be an option for the treatment of T2D-linked hyperglycemia.

The Role of Inositol Phosphate Multikinase (IPMK) in Time Restricted Feeding in Animal Model

Obesity is a major public health problem of the U.S. and is associated with diabetes, cardiovascular diseases and other diseases. Most research studies focus on excessive food consumption as the main cause of obesity. However, emerging data indicate that the timing of feeding can have significant effects on body weight and metabolism. Numerous studies in animals and small clinical studies in humans have shown that eating erratically over the 24 hour period or out of phase with the circadian rhythm predisposes toward weight gain, steatosis, dyslipidemia, insulin resistance and diabetes. Furthermore, studies indicate that restricting food intake to the active period synchronizes the circadian rhythm and metabolism, enhances weight loss and improves metabolic outcomes. Time restricted feeding (TRF) increases the amplitudes of clock gene expression and pathways mediating nutrient sensing and hepatic metabolism. However, the mechanisms mediating the effects of TRF are not fully understood. Here we characterized mice (10 week-old) fed a high-fat diet ad libitum (ALF) or from 7 pm to 7 am (TRF) for 2 weeks. The basal glucose production rate was similar between the two groups. Under hyperinsulinemic-euglycemic clamp, the glucose infusion rate (GIR) was significantly greater in TRF group compared to ALF group indicating an increase in insulin sensitivity. Using radioisotopic tracers, we demonstrated that the hepatic glucose production (HGP) was significantly reduced and the glucose disappearance rate was increased in TRF group compared to ALF group. Moreover, a biochemical analyses of liver tissues revealed that Inositol phosphate multikinase (IPMK) act as a key enzyme for inositol polyphosphate biosynthesis and play a role in insulin-, nutrient-, and energy-mediated metabolic signaling, was increased during TRF. Moreover, deletion of IPMK in hepatocytes decreased insulin stimulated AKT phosphorylation while increased lipid accumulation and gluconeogenesis. Importantly, hepatic deletion of IPMK attenuated the beneficial effects of TRF suggesting that IPMK in the liver may contributes to beneficial effects of TRF. Our findings provide the potential mechanism by which TRF confers the beneficial effects and may provide a novel therapeutic strategy for treating diabetes.

Adaptation of Insulin Clearance to Metabolic Demand Is a Key Determinant of Glucose Tolerance.

With the development of insulin resistance (IR), there is a compensatory increase in the plasma insulin response to offset the defect in insulin action to maintain normal glucose tolerance. The insulin response is the result of two factors: insulin secretion and metabolic clearance rate of insulin (MCRI). Subjects (104 with normal glucose tolerance [NGT], 57 with impaired glucose tolerance [IGT], and 207 with type 2 diabetes mellitus [T2DM]), divided in nonobese and obese groups, received a euglycemic insulin-clamp (40 mU/m2 ⋅ min) and an oral glucose tolerance test (OGTT) (75 g) on separate days. MCRI was calculated during the insulin-clamp performed with [3-3H]glucose and the OGTT and related to IR: peripheral (glucose uptake during the insulin clamp), hepatic (basal endogenous glucose production × fasting plasma insulin [FPI]), and adipocyte (fasting free fatty acid × FPI). MCRI during the insulin clamp was reduced in obese versus nonobese NGT (0.60 ± 0.03 vs. 0.73 ± 0.02 L/min ⋅ m2, P < 0.001), in nonobese IGT (0.62 ± 0.02, P < 0.004), and in nonobese T2DM (0.68 ± 0.02, P < 0.03). The MCRI during the insulin clamp was strongly and inversely correlated with IR (r = -0.52, P < 0.0001). During the OGTT, the MCRI was suppressed within 15-30 min in NGT and IGT subjects and remained suppressed. In contrast, suppression was minimal in T2DM. In conclusion, the development of IR in obese subjects is associated with a decline in MCRI that represents a compensatory response to maintain normal glucose tolerance but is impaired in individuals with T2DM.

Salicylate administration suppresses the inflammatory response to nutrients and improves ovarian function in polycystic ovary syndrome.

Oxidative stress (OS) and inflammation are often present in polycystic ovary syndrome (PCOS). We examined the effects of salsalate treatment on nutrient-induced OS and inflammation, ovarian androgen secretion, ovulation, and insulin sensitivity in PCOS. Eight lean insulin-sensitive women with PCOS and eight age- and body composition-matched ovulatory controls for baseline comparison participated in the study. The women with PCOS underwent a 12-wk treatment of salsalate, a nonsteroidal anti-inflammatory drug, at a dose of 3 g daily. Markers of OS and inflammation were quantified in mononuclear cells (MNC) and plasma from blood drawn fasting and 2 h after saturated fat ingestion before and after treatment. Ovarian androgen secretion was assessed from blood drawn fasting and 24, 48, and 72 h after human chorionic gonadotropin (HCG) administration before and after treatment. Ovulation was documented based on biphasic basal body temperatures and luteal range progesterone elevations. A two-step pancreatic clamp was performed pre- and posttreatment to measure basal endogenous glucose production (EGP) and the steady-state glucose disposal rate (GDR) during the euglycemic phase and markers of OS and inflammation in MNC and plasma during the hyperglycemic phase. Salsalate administration suppressed lipid- and glucose-stimulated reactive oxygen species generation, activated nuclear factor-κB and circulating tumor necrosis factor-α, normalized basal androgen levels, and lowered HCG-stimulated androgen secretion without altering EGP or GDR. Four salsalate-treated subjects responded with two consecutive ovulations. We conclude that in PCOS, salsalate-induced suppression of OS and inflammation ameliorates ovarian androgen hypersecretion and may induce ovulation while maintaining insulin action.

Clinical Parameters, Fuel Oxidation, and Glucose Kinetics in Patients With Type 2 Diabetes Treated With Dapagliflozin Plus Saxagliptin.

To examine the mechanisms responsible for improved glycemia with combined sodium-glucose cotransporter 2 inhibitor (SGLT2i) plus dipeptidyl peptidase 4 inhibitor therapy in type 2 diabetes. Fifty-six patients (HbA1c 8.9 ± 0.2% [74 ± 2 mmol/mol]) were randomized to dapagliflozin (DAPA) 10 mg, DAPA/saxagliptin (SAXA) 10/5 mg, or placebo (PCB) for 16 weeks. Basal endogenous glucose production (EGP) (3-3H-glucose), urinary glucose excretion, glucose/lipid oxidation, HbA1c, and substrate/hormone levels were determined before treatment (Pre-Tx) and after treatment (Post-Tx). At week 16, HbA1c decrease was greater (P < 0.05) in DAPA/SAXA (-2.0 ± 0.3%) vs. DAPA (-1.4 ± 0.2%) and greater than PCB (0.2 ± 0.2%). Day 1 of drug administration, EGP (∼2.40 mg/kg/min) decreased by -0.44 ± 0.09 mg/kg/min in PCB (P < 0.05) but only by -0.21 ± 0.02 mg/kg/min in DAPA and DAPA/SAXA (P < 0.05 vs. PCB). At week 16, EGP increased to 2.67 ± 0.09 mg/kg/min (DAPA) and 2.61 ± 0.08 mg/kg/min (DAPA/SAXA), despite reductions in fasting plasma glucose by 47 and 77 mg/dL, respectively, and no changes in PCB. Baseline plasma free fatty acids rose by 40 µmol/L with DAPA but declined by -110 with PCB and -90 µmol/L with DAPA/SAXA (P < 0.05, Pre-Tx vs. Post-Tx). In DAPA, carbohydrate oxidation rates decreased from 1.1 ± 0.1 to 0.7 ± 0.1 mg/kg/min, whereas lipid oxidation rates increased from 0.6 ± 0.1 to 0.8 ± 0.1 mg/kg/min (P < 0.01). In DAPA/SAXA, the shift in carbohydrate (1.1 ± 0.1 to 0.9 ± 0.1 mg/kg/min) and lipid (0.6 ± 0.1 to 0.7 ± 0.1 mg/kg/min) oxidation was attenuated (P < 0.05). The addition of SAXA to DAPA resulted in superior glycemic control compared with DAPA monotherapy partly because of increased glucose utilization and oxidation. Although the decrease in insulin/glucagon ratio was prevented by SAXA, EGP paradoxical elevation persisted, indicating that other factors mediate EGP changes in response to SGLT2i-induced glucosuria.

1326-P: Metformin Increases GLP-1 Concentrations and Improves Glycemia in Youth with Type 2 Diabetes

Metformin is the only approved oral agent for youth with type 2 diabetes (T2D), but its mechanism of action remains controversial. Recent data suggests a primary role for the entero-insular instead of the gluconeogenic pathway, but there is no data in youth, in whom metformin efficacy is ∼50%. Our objectives were to: (1) compare incretin concentrations, glucagon-like 1 peptide (GLP-1) and gastric inhibitory polypeptide (GIP) in 12 youth with T2D not on metformin to 10 healthy age and BMI-matched controls, and (2) determine the change in incretins and gluconeogenesis (GNG) after 3 months of metformin in 8 youth with T2D. Intact GLP-1 and total GIP were measured at 0 and 2-hour during a 75g OGTT and basal GNG (2H20) and glucose production (6,62H2glucose) measured after an overnight fast. Compared to controls, youth with T2D before metformin had higher HbA1c and glucose levels and lower fasting and 2-hour GLP-1 (P&amp;lt;0.05 Table). After metformin, HbA1c decreased and fasting GLP-1 increased but there was no change in BMI, GNG or glucose production (P&amp;gt;0.1 Table). Post-metformin GLP-1 was comparable to levels in controls (P&amp;gt;0.1). There was no difference in GIP between youth with and without T2D and no change with metformin. Overall, improved glycemic control with short-term metformin in youth was associated with increased GLP-1 concentrations independent of changes in BMI and GNG supporting an entero-insular mechanistic pathway. Disclosure C.K. Cravalho: None. A.G. Meyers: None. L. Mabundo: None. A.B. Courville: None. S. Bernstein: None. Y. Dai: None. M. Walter: None. S. Chacko: None. M.W. Haymond: Advisory Panel; Self; Daiichi Sankyo Company, Limited, Zealand Pharma A/S. Stock/Shareholder; Self; Xeris Pharmaceuticals, Inc. Other Relationship; Self; AstraZeneca. S.T. Chung: None. Funding National Institute of Diabetes and Digestive and Kidney Diseases

Comparing Liver And Skeletal Muscle Sensitivity In Response To Acute And Chronic Calorie Restriction

PURPOSE: We determined the effects of acute and chronic calorie restriction on hepatic and skeletal muscle insulin sensitivity. METHODS: Twenty-three obese subjects (body-mass index, 36.3±0.7kg/m2) followed an energy-deficit diet (1,200kcals/day). Magnetic resonance spectroscopy, muscle biopsies, and a euglycemic-hyperinsulinemic clamp were used to determine insulin action, cellular insulin signaling and intrahepatic triglyceride content before, after 48-h, and after ~12 wks (7% weight loss) of diet therapy. RESULTS: Intrahepatic triglyceride content significantly decreased at both 48-h (-16.6±2.3%, p<0.001) and 7% weight loss (-40.7 ± 6.2%; p<0.001) compared to baseline. Basal glucose production rate significantly decreased at 48-h (-21.8±3.2%, p<0.001) and after 7% weight loss (-20.8±3.4%, p<0.001). Insulin-mediated glucose uptake did not significantly change at 48-h (-5.2±12.8%, p>0.05) but did significantly increase at 7% weight loss (26.1 ± 4.3%, p<0.05). Insulin-stimulated phosphorylation of Jun N-terminal kinase did not change at 48-h (-0.2 ± 16.2%, p>0.05) but did significantly decrease at 7% weight loss (-29.9 ± 12.6, p<0.05) and phosphorylation of Akt increased by 15.2 ± 14.6% (p>0.05) and 36.2 ± 8.8%,(p<0.05), after 48-h and 7% weight loss, respectively. CONCLUSION: A low calorie diet acutely reduced intrahepatic triglyceride content and improved hepatic insulin sensitivity whereas moderate weight loss is necessary to improve insulin sensitivity in the skeletal muscle.

OR07-3 Validation of Surrogate Models to Assess Tissue and Whole-Body Insulin Resistance Among High-Risk Adolescent Girls

Polycystic Ovarian Syndrome (PCOS) is a common endocrine disorder which develops in adolescence and affects 6-10% of women. PCOS is associated with insulin resistance (IR), which can occur in multiple tissues, in particular skeletal muscle and liver. Reliable assessment of tissue-specific IR in youth with PCOS is important for development of new therapies. The gold-standard method to assess tissue-IR is the hyper-insulinemic euglycemic clamp, a method which is too intensive for use in routine research. We aimed to validate surrogate indices (the oral minimal model (OMM)-derived whole-body index and the Abdul-Ghani model-derived muscle index and liver index) against their respective clamp measurements in a population of high-IR-risk adolescent girls. 45 adolescent girls (14.6 ± 1.7 years; BMI %ile 23.3%-98.2%) underwent a standard 2-hour oral glucose tolerance test (OGTT) (75g glucose) and a multi-phase hyper-insulinemic euglycemic clamp (10,16 and 80 mU/m2/min) with a glucose isotope tracer. This study was a secondary analysis. OMM total Si was computed using SAAM II software, using 0, 15, 30, 60, 90, 120 min time points and the assumption that glucose rate of appearance (Ra) decays exponentially after 120 min. Abdul-Ghani muscle and liver insulin resistance indices (IRIs) were calculated: liver IRI= AUC0-30min Glucose (mmol L-1 min) x AUC0-30min Insulin (pmol L-1 min); muscle IRI= mean insulin0-120min. Correlation analyses were performed using Spearman’s or Pearson’s correlation, as appropriate. OMM total Si correlated with clamp-measured insulin sensitivity (glucose infusion rate, r=0.65; p<0.0001), whereas muscle IRI did not (p=0.45). Liver IRI correlated moderately with clamp-derived hepatic insulin sensitivity (insulin concentration required to suppress 50% of basal endogenous glucose production; r=0.35; p=0.03). In adolescent girls at high risk of IR, OMM provided a strong surrogate characterization of whole-body IR when evaluated against the clamp. The Abdul-Ghani model indices are simpler to calculate compared to OMM; however, these results suggest that the Abdul-Ghani indices may not be adequate for describing and distinguishing among individuals within a narrower IR range, such as that found in our study population. By contrast, OMM offers an effective, OGTT-based methodology to be used in research studies for characterizing whole-body IR that is less resource-intensive compared to the clamp. Future work is needed to determine if the sensitivity of this model can be further improved with a longer-duration OGTT as obese youth can have an exaggerated and prolonged response to an OGTT. Funding: Thrasher Research Foundation, AHA CRP, Endocrine Society Fellowship in Women's Health, NIDDK K23

Differential effects of metformin glycinate and hydrochloride in glucose production, AMPK phosphorylation and insulin sensitivity in hepatocytes from non-diabetic and diabetic mice

The liver is a main target tissue of the biguanide metformin which activates AMP-activated protein kinase (AMPK). We previously reported that administration of metformin glycinate showed a greater decrease of glycated hemoglobin A1c than a placebo in patients with type 2 diabetes mellitus (T2DM). In this study, we compared the effects of metformin hydrochloride, the oral antidiabetic drug of first choice, with those of metformin glycinate in hepatocytes from non-diabetic and diabetic mice and humans. Both formulations were equally potent regard to the reduction of basal and glucagon-induced glucose production and mRNA levels of gluconeogenic enzymes (Pck1 and G6pc) in hepatocytes from C57/Bl6 mice and humans. On the contrary, phosphorylation of AMPK and its substrate acetyl CoA carboxylase (ACC) was faster in hepatocytes treated with metformin glycinate. Likewise, we found stronger reduction in hepatocytes from obese/diabetic db/db mice of glucagon-induced glucose output and more sustained AMPK phosphorylation after treatment with metformin glycinate. Importantly, insulin sensitization regarding phosphorylation of AKT (Ser473) was enhanced in hepatocytes from db/db mice or humans pretreated with metformin glycinate. In conclusion, our data indicate that metformin glycinate may be an alternative therapy against insulin resistance during obesity and/or T2DM.

Gluconeogenesis and risk for fasting hyperglycemia in Black and White women.

Black women, compared with White women, have high rates of whole-body insulin resistance but a lower prevalence of fasting hyperglycemia and hepatic steatosis. This dissociation of whole-body insulin resistance from fasting hyperglycemia may be explained by racial differences in gluconeogenesis, hepatic fat, or tissue-specific insulin sensitivity. Two groups of premenopausal federally employed women, without diabetes were studied. Using stable isotope tracers, [2H2O] and [6,62-H2]glucose, basal glucose production was partitioned into its components (gluconeogenesis and glycogenolysis) and basal whole-body lipolysis ([2H5]glycerol) was measured. Indices of insulin sensitivity, whole-body (SI), hepatic (HISIGPR), and adipose tissue, were calculated. Hepatic fat was measured by proton magnetic resonance spectroscopy. Black women had less hepatic fat and lower fractional and absolute gluconeogenesis. Whole-body SI, HISIGPR, and adipose tissue sensitivity were similar by race, but at any given level of whole-body SI, Black women had higher HISIGPR. Therefore, fasting hyperglycemia may be a less common early pathological feature of prediabetes in Black women compared with White women, because gluconeogenesis remains lower despite similar whole-body SI.

Effect of Chronic Hyperglycemia on Glucose Metabolism in Subjects With Normal Glucose Tolerance.

Chronic hyperglycemia causes insulin resistance, but the inheritability of glucotoxicity and the underlying mechanisms are unclear. We examined the effect of 3 days of hyperglycemia on glucose disposal, enzyme activities, insulin signaling, and protein O-GlcNAcylation in skeletal muscle of individuals without (FH−) or with (FH+) family history of type 2 diabetes. Twenty-five subjects with normal glucose tolerance received a [3-3H]glucose euglycemic insulin clamp, indirect calorimetry, and vastus-lateralis biopsies before and after 3 days of saline (n = 5) or glucose (n = 10 FH− and 10 FH+) infusion to raise plasma glucose by ∼45 mg/dL. At baseline, FH+ had lower insulin-stimulated glucose oxidation and total glucose disposal (TGD) but similar nonoxidative glucose disposal and basal endogenous glucose production (bEGP) compared with FH−. After 3 days of glucose infusion, bEGP and glucose oxidation were markedly increased, whereas nonoxidative glucose disposal and TGD were lower versus baseline, with no differences between FH− and FH+ subjects. Hyperglycemia doubled skeletal muscle glycogen content and impaired activation of glycogen synthase (GS), pyruvate dehydrogenase, and Akt, but protein O-GlcNAcylation was unchanged. Insulin resistance develops to a similar extent in FH− and FH+ subjects after chronic hyperglycemia, without increased protein O-GlcNAcylation. Decreased nonoxidative glucose disposal due to impaired GS activation appears to be the primary deficit in skeletal muscle glucotoxicity.

Dietary Rapeseed Oil Supplementation Reduces Hepatic Steatosis in Obese Men

Obesity is associated with nonalcoholic fatty liver disease (NAFLD) leading to increased hepatic glucose production. NAFLD is one of the most frequent liver diseases however, effective treatment is limited. Animal studies showed a reduction in hepatic steatosis with dietary alpha linoleic acid, which is highly enriched in rapeseed oil (RA). In this study we used a nutritional therapeutic approach and investigated the effect of an isocaloric diet supplemented with RA or olive oil (OL) on liver fat content, endogenous glucose production, total body insulin sensitivity and serum lipids in obese humans suffering from NAFLD. 27 obese men (BMI 30-35, age 18-65) consumed an isocaloric diet including 50 g of either RA (n=12) or OL (n=15) daily for eight weeks. Hepatic MRI, hyperinsulinemic-euglycemic clamp studies with isotope labelled glucose and blood tests were performed prior to and at the end of the study to assess liver fat content, endogenous glucose production and cholesterol and free fatty acid levels, respectively. Body fat content and BMI did not change over the time of intervention for RA and OL. At the end of the study a significant reduction in hepatic fat content (P=0.038) could be observed for RA (13.09±1.61 before vs. 11.14±1.58% after intervention) vs. OL (13.29±2.52 before vs. 15.73±2.74% after intervention). For RA, a 21% reduction (P&amp;lt;0.02) in serum free fatty acids was observed after eight weeks of oil consumption whereas no significant changes were seen for OL. Consuming RA resulted in a slight reduction in basal endogenous glucose production (1.71±0.15 before vs. 1.49±0.mg/kg/min after intervention, P=n.s.) compared to OL (1.66±0.before vs. 1.65±0.mg/kg/min after intervention, P=n.s.). There were no significant changes in total body insulin sensitivity and serum cholesterol levels in RA or OL. Our results demonstrate a beneficial effect of the fatty acid composition of RA on hepatic lipid production as shown by reduced hepatic fat content and free fatty acid levels. Disclosure M. Kruse: None. M. Kemper: None. S. Gancheva: None. D. Dannenberger: None. D.F. Markgraf: None. M. Roden: Speaker's Bureau; Self; Boehringer Ingelheim GmbH. Research Support; Self; Boehringer Ingelheim GmbH. Consultant; Self; Poxel SA. Research Support; Self; Danone Nutricia Early Life Nutrition, GlaxoSmithKline plc., Nutricia Advanced Medical Nutrition, Sanofi. A.F. Pfeiffer: None.

Increased Gluconeogenesis Is Not an Early Feature of Whole-Body Insulin Resistance in Black Women—The Federal Women Study

In contrast to white women, fasting hyperglycemia is not an early diabetes risk marker in black women. The etiology of this racial difference in risk is unknown but could be related to differences in rates of gluconeogenesis and hepatic fat in black women. Using stable isotope tracers [2H2O], [6,62H2]glucose, and ([2H5]glycerol), we partitioned basal glucose production into its two components (gluconeogenesis and glycogenolysis) and measured basal whole body lipolysis. Whole body (SI), hepatic (HIS) and adipose tissue insulin sensitivity were calculated in two groups of federally employed pre-menopausal women, without diabetes: 24 black and 19 white; age 37±6 (mean±SD), range 25-50y; BMI 33±6, range 24.9-45.2 kg/m2. Hepatic and visceral fat were measured by proton MRS. The prevalence of prediabetes (17% vs. 26%), age and BMI were similar in blacks and whites, all P&amp;gt;0.4). Black women had less fasting hyperglycemia (4% vs. 22%, P=0.1), lower visceral and hepatic fat (P&amp;lt;0.01) but similar SI, adipose tissue insulin sensitivity and whole body lipolysis (all P&amp;gt;0.5). Basal glucose, insulin and FFA concentrations were similar in both groups (P&amp;gt;0.05). Blacks had lower glucose production (2.52±0.34 vs. 2.75±0.28 mg·kglbm-1·min-1, P&amp;lt;0.05), fractional gluconeogenesis (57.6±10.6 vs. 66.3±11.4%, P=0.02), and absolute gluconeogenesis (1.44±0.28 vs. 1.77±0.31 mg·kglbm-1·min-1, P&amp;lt;0.01). HIS correlated with SI and hepatic fat (both r=0.5, P&amp;lt;0.01) and the relationship did not differ by race (P&amp;gt;0.05). However, at the same SI blacks had higher HIS (intercepts P&amp;lt;0.01). In summary, black women had relatively preserved HIS and lower hepatic fat, while white women had higher gluconeogenesis and hepatic fat associated with fasting hyperglycemia. Fasting glucose may be a poor early diabetes marker in black women because gluconeogenesis was low despite whole-body insulin resistance. Disclosure S.T. Chung: None. M.W. Haymond: Advisory Panel; Self; Zealand Pharma A/S. Other Relationship; Self; Xeris Pharmaceuticals, Inc.. A. Onuzuruike: None. L. Mabundo: None. H. Garraffo: None. P.J. Walter: None. A.B. Courville: None. A.M. Gharib: None. S. Chacko: None. A.E. Sumner: None.

Changes In Liver And Skeletal Muscle Sensitivity In Response To Acute And Chronic Calorie Restriction On A Low Carbohydrate Diet

PURPOSE: We determined the effects of acute and chronic calorie restriction with a low-carbohydrate diet on hepatic and skeletal muscle insulin sensitivity. METHODS: Twelve obese subjects (body-mass index, 36.1±1.0kg/m2) followed a low-carbohydrate (<60g/d) energy-deficit diet (1,200kcals/day). Magnetic resonance spectroscopy, muscle biopsies, and a euglycemic-hyperinsulinemic clamp were used to determine insulin action, cellular insulin signaling and intrahepatic triglyceride content before, after 48 h, and after ~12 wks (7% weight loss) of diet therapy. RESULTS: Intrahepatic triglyceride content significantly decreased at both 48-h (28.6±3.8%) and 7% weight loss (-38.0 ± 4.5%; p<0.05) compared to baseline. Basal glucose production rate significantly decreased at 48 h (21.8±3.2%, p<0.001) and after 7% weight loss (20.8±3.4%, p<0.001). Insulin- mediated glucose uptake did not significantly increase at 48 h (4.4±12.7%, p>0.05) but did significantly increase at 7% weight loss (35.2 ± 8.4%, p<0.05). Insulin-stimulated phosphorylation of Jun N-terminal kinase decreased by (-15.4 ± 18.1%, p>0.05) and -41.3 ± 19.5, p<0.05) and phosphorylation of Akt increased by 19.2 ± 26.9% (p>0.05) and 36.1 ± 12.4%,(p<0.05), after 48-h and 7% weight loss respectively. CONCLUSIONS: A low carbohydrate calorie diet acutely reduced intrahepatic triglyceride content and improved hepatic insulin sensitivity whereas moderate weight loss is necessary to improve insulin sensitivity in the skeletal muscle.

Acute activation of GLP-1-expressing neurons promotes glucose homeostasis and insulin sensitivity

ObjectiveGlucagon-like peptides are co-released from enteroendocrine L cells in the gut and preproglucagon (PPG) neurons in the brainstem. PPG-derived GLP-1/2 are probably key neuroendocrine signals for the control of energy balance and glucose homeostasis. The objective of this study was to determine whether activation of PPG neurons per se modulates glucose homeostasis and insulin sensitivity in vivo. MethodsWe generated glucagon (Gcg) promoter-driven Cre transgenic mice and injected excitatory hM3Dq-mCherry AAV into their brainstem NTS. We characterized the metabolic impact of PPG neuron activation on glucose homeostasis and insulin sensitivity using stable isotopic tracers coupled with hyperinsulinemic euglycemic clamp. ResultsWe showed that after ip injection of clozapine N-oxide, Gcg-Cre lean mice transduced with hM3Dq in the brainstem NTS downregulated basal endogenous glucose production and enhanced glucose tolerance following ip glucose tolerance test. Moreover, acute activation of PPG neuronsNTS enhanced whole-body insulin sensitivity as indicated by increased glucose infusion rate as well as augmented insulin-suppression of endogenous glucose production and gluconeogenesis. In contrast, insulin-stimulation of glucose disposal was not altered significantly. ConclusionsWe conclude that acute activation of PPG neurons in the brainstem reduces basal glucose production, enhances intraperitoneal glucose tolerance, and augments hepatic insulin sensitivity, suggesting an important physiological role of PPG neurons-mediated circuitry in promoting glycemic control and insulin sensitivity.

Early-onset obesity and food restriction alter hepatocyte metabolism in adult Wistar rats

Context: Caloric restriction (CR) is suggested for overweight control.Objective: Systemic and liver glucose metabolism in the reduced-litter (RL) rat model under 30% CR was investigated.Materials and methods: Newborn litters were organised in control (G9); RL with free diet (G3L); and RL with CR (G3R). Assessments were made at the age of 90 d.Results: Higher liver glycogen content and changes in systemic glucose handling were found in the RL groups. Hepatocyte glucose metabolism was similar in groups G9 and G3L, but basal glucose production and glycogenolysis were higher, while gluconeogenesis and basal glycolysis were lower in the G3R. Urea production was lower in the RL groups.Discussion: The altered glucose handling of the RL adult rats was not reversed by moderate (30%) CR. Hepatocyte glucose and nitrogen metabolism were changed by both early overfeeding and current feeding conditions.Conclusions: RL and CR alter systemic and liver glucose metabolism.

Capparis spinosa L. aqueous extract evokes antidiabetic effect in streptozotocin-induced diabetic mice.

As the aqueous extract of Capparis spinosa (CS) possess antidiabetic effect, he present study aims to reveal the possible mechanism of action of CS in diabetic mice. Both single and repeated oral administrations of aqueous extract of CS were performed in multi-low dose streptozotocin-induced (MLDS) diabetic mice. Euglycemic hyperinsulinemic clamp was used in association with the endogenous glucose production (perfusion rate of 3-3H glucose) to evaluate the effect of CS aqueous extract on insulin sensitivity. Our study showed that aqueous extract of CS possess a potent hypoglycaemic activity in MLDS diabetic mice. Furthermore, the analysis perfusion of 3-3H glucose demonstrated the parallel decrease of basal endogenous glucose production (EGP) with the hypoglycaemic activity. EGP was lower in CS-Treated group when compared to the control group (p<0.001). The euglycemic hyperinsulinemic clamp technique demonstrated that CS treatment improves insulin sensitivity in peripheral tissues. We conclude that the antihyperglycemic effet CS is probably due to the inhibition of basal endogenous glucose production and the improvement of insulin sensitivity in MLDS diabetic mice.

Quantifying rates of glucose production in vivo following an intraperitoneal tracer bolus.

Aberrant regulation of glucose production makes a critical contribution to the impaired glycemic control that is observed in type 2 diabetes. Although isotopic tracer methods have proven to be informative in quantifying the magnitude of such alterations, it is presumed that one must rely on venous access to administer glucose tracers which therein presents obstacles for the routine application of tracer methods in rodent models. Since intraperitoneal injections are readily used to deliver glucose challenges and/or dose potential therapeutics, we hypothesized that this route could also be used to administer a glucose tracer. The ability to then reliably estimate glucose flux would require attention toward setting a schedule for collecting samples and choosing a distribution volume. For example, glucose production can be calculated by multiplying the fractional turnover rate by the pool size. We have taken a step-wise approach to examine the potential of using an intraperitoneal tracer administration in rat and mouse models. First, we compared the kinetics of [U-13C]glucose following either an intravenous or an intraperitoneal injection. Second, we tested whether the intraperitoneal method could detect a pharmacological manipulation of glucose production. Finally, we contrasted a potential application of the intraperitoneal method against the glucose-insulin clamp. We conclude that it is possible to 1) quantify glucose production using an intraperitoneal injection of tracer and 2) derive a "glucose production index" by coupling estimates of basal glucose production with measurements of fasting insulin concentration; this yields a proxy for clamp-derived assessments of insulin sensitivity of endogenous production.

The vitamin D metabolites 25(OH)D and 1,25(OH)2D are not related to either glucose metabolism or insulin action in obese women

AimVitamin D deficiency has been proposed to be involved in obesity-induced metabolic disease. However, data on the relationship between 25-hydroxycholecalciferol (25(OH)D) and insulin resistance have been inconsistent, and few studies have investigated the active vitamin D metabolite, 1,25-dihydroxycholecalciferol (1,25(OH)2D). This study aimed to determine the relationship between circulating levels of both 25(OH)D and 1,25(OH)2D and direct measures of glucose metabolism and insulin action in obese women. MethodsSerum levels of 25(OH)D and 1,25(OH)2D, and glucose metabolism and tissue-specific insulin action, as assessed in the basal state and during a two-step euglycaemic–hyperinsulinaemic clamp study with [6,6-2H2]glucose infusion, were measured in 37 morbidly obese women (age: 43±10 years; body mass index: 44±6kg/m2). ResultsSixteen subjects had circulating 25(OH)D levels<50nmol/L, consistent with vitamin D deficiency, and 21 had normal 25(OH)D levels. There were no differences in either baseline characteristics or parameters of glucose metabolism and insulin action between the groups. Serum 25(OH)D, but not 1,25(OH)2D, was negatively correlated with both body mass index (r=−0.42, P=0.01) and total body fat (r=−0.46, P<0.01). Neither 25(OH)D nor 1,25(OH)2D levels were related to any measured metabolic parameters, including fasting glucose, fasting insulin, basal endogenous glucose production, and hepatic, adipose-tissue and skeletal muscle insulin sensitivity. ConclusionObesity was associated with lower levels of circulating 25(OH)D, but not with the hormonally active metabolite 1,25(OH)2D. Neither 25(OH)D nor 1,25(OH)2D were related to glucose metabolism and tissue-specific insulin sensitivity in obese women, suggesting that vitamin D does not play a major role in obesity-related insulin resistance.

Investigation of salicylate hepatic responses in comparison with chemical analogues of the drug

Anti-hyperglycaemic effects of the hydroxybenzoic acid salicylate might stem from effects of the drug on mitochondrial uncoupling, activation of AMP-activated protein kinase, and inhibition of NF-κB signalling. Here, we have gauged the contribution of these effects to control of hepatocyte glucose production, comparing salicylate with inactive hydroxybenzoic acid analogues of the drug. In rat H4IIE hepatoma cells, salicylate was the only drug tested that activated AMPK. Salicylate also reduced mTOR signalling, but this property was observed widely among the analogues. In a sub-panel of analogues, salicylate alone reduced promoter activity of the key gluconeogenic enzyme glucose 6-phosphatase and suppressed basal glucose production in mouse primary hepatocytes. Both salicylate and 2,6 dihydroxybenzoic acid suppressed TNFα-induced IκB degradation, and in genetic knockout experiments, we found that the effect of salicylate on IκB degradation was AMPK-independent. Previous data also identified AMPK-independent regulation of glucose but we found that direct inhibition of neither NF-κB nor mTOR signalling suppressed glucose production, suggesting that other factors besides these cell signalling pathways may need to be considered to account for this response to salicylate. We found, for example, that H4IIE cells were exquisitely sensitive to uncoupling with modest doses of salicylate, which occurred on a similar time course to another anti-hyperglycaemic uncoupling agent 2,4-dinitrophenol, while there was no discernible effect at all of two salicylate analogues which are not anti-hyperglycaemic. This finding supports much earlier literature suggesting that salicylates exert anti-hyperglycaemic effects at least in part through uncoupling.