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Type 2 diabetes is characterized by fasting hyperglycemia, secondary to hepatic insulin resistance and increased glucose production. Peroxisome proliferator-activated receptor-[gamma] coactivator-1[alpha] (PGC-1[alpha]) is a transcriptional coactivator that is thought to control adaptive responses to physiological stimuli. In liver, PGC-1[alpha] expression is induced by fasting, and this effect promotes gluconeogenesis. To examine whether PGC-1[alpha] is involved in the pathogenesis of hepatic insulin resistance, we generated transgenic (TG) mice with whole body overexpression of human PGC-1[alpha] and evaluated glucose homeostasis with a euglycemic-hyperinsulinemic clamp. PGC-1[alpha] was moderately (~2-fold) overexpressed in liver, skeletal muscle, brain, and heart of TG mice. In liver, PGC-l[alpha] overexpression resulted in increased expression of hepatocyte nuclear factor-4[alpha] and the gluconeogenic enzymes phosphoenolpyruvate carboxykinase and glucose-6-phosphatase. PGC-1[alpha] overexpression caused hepatic insulin resistance, manifested by higher glucose production and diminished insulin suppression of gluconeogenesis. Paradoxically, PGC-1[alpha] overexpression improved muscle insulin sensitivity, as evidenced by elevated insulin-stimulated Akt phosphorylation and peripheral glucose disposal. Content of myoglobin and troponin I slow protein was increased in muscle of TG mice, indicating fiber-type switching. PGC-1[alpha] overexpression also led to lower reactive oxygen species production by mitochondria and reduced IKK/I[kappa]B signaling in muscle. Feeding a high-fat diet to TG mice eliminated the increased muscle insulin sensitivity. The dichotomous effect of PGC-1[alpha] overexpression in liver and muscle suggests that PGC-1[alpha] is a fuel gauge that couples energy demands (muscle) with the corresponding fuel supply (liver). Thus, under conditions of physiological stress (i.e., prolonged fast and exercise training), increased hepatic glucose production may help sustain glucose utilization in peripheral tissues. diabetes; phosphoenolpyruvate carboxykinase; glucose-6-phosphatase; gluconeogenesis

Insulin resistance is a characteristic feature of type 2 diabetes and obesity. Insulin-resistant individuals manifest multiple disturbances in free fatty acid (FFA) metabolism and have excessive lipid accumulation in insulin target tissues. Although much evidence supports a causal role for altered FFA metabolism in the development of insulin resistance, i.e., 'lipotoxicity', the intracellular mechanisms by which elevated plasma FFA levels cause insulin resistance have yet to be completely elucidated. Recent studies have implicated a possible role for mitochondrial dysfunction in the pathogenesis of insulin resistance in skeletal muscle. We examined the effect of FFA metabolites [palmitoyl carnitine (PC), palmitoyl-coenzyme A (CoA), and oleoyl-CoA] on ATP synthesis in mitochondria isolated from mouse and human skeletal muscle. At concentrations ranging from 0.5 to 2 [micro]M, these FFA metabolites stimulated ATP synthesis; however, above 5 [micro]M, there was a dose-response inhibition of ATP synthesis. Furthermore, 10 [micro]M PC inhibits ATP synthesis from pyruvate. Elevated PC concentrations ([greater than or equal to] 10 [micro]M) inhibit electron transport chain activity and decrease the mitochondrial inner membrane potential. These acquired mitochondrial defects, caused by a physiological increase in the concentration of FFA metabolites, provide a mechanistic link between lipotoxicity, mitochondrial dysfunction, and muscle insulin resistance. palmitoyl carnitine; palmitoyl-coenzyme A; oleoyl-coenzyme A; mitochondria; adenosine 5'-triphosphate synthesis; insulin resistance; type 2 diabetes

This study was undertaken to test the hypothesis that short-term exposure (4 h) to physiological hyperinsulinemia in normal, healthy subjects without a family history of diabetes would induce a low grade inflammatory response independently of glycemic status. Twelve normal glucose tolerant subjects received a 4-h euglycemic hyperin-sulinemic clamp with biopsies of the vastus lateralis muscle. Microarray analysis identified 121 probe sets that were significantly altered in response to physiological hyperinsulinemia while maintaining euglycemia. In normal, healthy human subjects insulin increased the mRNAs of a number of inflammatory genes (CCL2, CXCL2 and THBD) and transcription factors (ATF3, BHLHB2, HES1, KLF10, JUNB, FOS, and FOSB). A number of other genes were upregulated in response to insulin, including RRAD, MT, and SGK. CITED2, a known coactivator of PPAR[alpha], was significantly downregulated. SGK and CITED2 are located at chromosome 6q23, where we previously detected strong linkage to fasting plasma insulin concentrations. We independently validated the mRNA expression changes in an additional five subjects and closely paralleled the results observed in the original 12 subjects. A saline infusion in healthy, normal glucosetolerant subjects without family history of diabetes demonstrated that the genes altered during the euglycemic hyperinsulinemic clamp were due to hyperinsulinemia and were unrelated to the biopsy procedure per se. The results of the present study demonstrate that insulin acutely regulates the levels of mRNAs involved in inflammation and transcription and identifies several candidate genes, including HES1 and BHLHB2, for further investigation. gene expression; muscle; insulin action; euglycemic hyperinsulinemic clamp; inflammation

A study to evaluate the efficacy of pioglitazone in the treatment of nonalcoholic steatohepatitis is conducted. Results confirm the effectiveness of pioglitazone as a form of treatment for nonalcoholic steatohepatitis and suggest further trials to assess the long-term benefits.

Purpose: Explore the extent to which heart failure (HF) symptoms and side effects of HF treatment experienced by patients are recognized by cardiologists, and concordance between patient-cardiologist perceptions of HF severity and patients' contributions to treatment decision-making.Methods: A multinational, cross-sectional survey of cardiologists and patients with HF was conducted. Patient-record forms (PRFs) were completed by cardiologists for consecutive consulting patients with HF, who completed a patient self-completion questionnaire (PSC). Responses from PRFs with an associated PSC were analyzed to compare patient- and cardiologist-reported occurrences of HF symptoms and treatment side effects, patient-perceived severity of HF and cardiologists' perceived risk of death within 12 months, and patient input into treatment decisions. Concordance was calculated as the number of response agreements between PSCs and PRFs for total number of matched pairs. Over- or underreporting of symptoms and side effects by cardiologists relative to patient-reported occurrences were calculated.Results: Overall, 2,454 patient-cardiologist pairs were identified. High levels of concordance between matched pairs were observed for the occurrence of reported HF symptoms (93%), side effects (77%-98%) and degree of patient input into treatment decisions (74%); for perceived HF severity, concordance was 54%. Most symptoms (except dyspnea when active and fatigue/weakness, experienced by >50% of patients) were underreported by cardiologists. Of patients reporting to have been informed by their cardiologist that their HF was mild, 28% were perceived by their cardiologist to have a moderate-high/very high risk of death within 12 months. Treatment choice was not discussed with almost a third of patients. When discussed, 94% of patients (n=1,540) reported the cardiologist made the final decision. Cardiologists more often under- than overreported the occurrence of side effects reported by patients.Conclusion: Improved patient-cardiologist dialogue and shared decision-making is required for optimizing patient care and outcomes in HF. [ABSTRACT FROM AUTHOR]

Type 2 diabetes is characterized by fasting hyperglycemia, secondary to hepatic insulin resistance and increased glucose production. Peroxisome proliferator-activated re- ceptor-γ coactivator-1α (PGC-1α) is a transcriptional coactivator that is thought to control adaptive responses to physiological stimuli. In liver, PGC-1α expression is induced by fasting, and this effect promotes gluconeogenesis. To examine whether PGC-1α is involved in the pathogenesis of hepatic insulin resistance, we generated transgenic (TO) mice with whole body overexpression of human PGC-1α and evaluated glucose homeostasis with a euglycemic-hyperinsulinemic clamp. PGC-1α was moderately (~P2-fold) overexpressed in liver, skeletal muscle, brain, and heart of TO mice. In liver, PGC-1α overexpression resulted in increased expression of hepatocyte nuclear factor-4α and the gluconeogenic enzymes phosphoeno/pyruvate carboxykinase and glucose-6-phosphatase. PGC-1α overexpression caused hepatic insulin resistance, manifested by higher glucose production and diminished insulin suppression of gluconeogenesis. Paradoxically, PGC-1α overexpression improved muscle insulin sensitivity, as evidenced by elevated insulin-stimulated Akt phosphorylation and peripheral glucose disposal. Content of myoglobin and troponin I slow protein was increased in muscle of TO mice, indicating fiber-type switching. PGC-1α overexpression also led to lower reactive oxygen species production by mitochondria and reduced 1KK/1κB signaling in muscle. Feeding a high-fat diet to TO mice eliminated the increased muscle insulin sensitivity. The dichotomous effect of POC-1α overexpression in liver and muscle suggests that PGC-1α is a fuel gauge that couples energy demands (muscle) with the corresponding fuel supply (liver). Thus, under conditions of physiological stress (i.e., prolonged fast and exercise training), increased hepatic glucose production may help sustain glucose utilization in peripheral tissues. [ABSTRACT FROM AUTHOR]

Grb10 is a pleckstrin homology and Src homology 2 domain-containing protein that interacts with a number of phosphorylated receptor tyrosine kinases, including the insulin receptor. In mice, Grb10 gene expression is imprinted with maternal expression in all tissues except the brain. While the interaction between Grb10 and the insulin receptor has been extensively investigated in cultured cells, whether this adaptor protein plays a positive or negative role in insulin signaling and action remains controversial. In order to investigate the in vivo role of Grb10 in insulin signaling and action in the periphery, we generated Grb10 knockout mice by the gene trap technique and analyzed mice with maternal inheritance of the knockout allele. Disruption of Grb10 gene expression in peripheral tissues had no significant effect on fasting glucose and insulin levels. On the other hand, peripheral-tissue-specific knockout of Grb10 led to significant overgrowth of the mice, consistent with a role for endogenous Grb10 as a growth suppressor. Loss of Grb10 expression in insulin target tissues, such as skeletal muscle and fat, resulted in enhanced insulin-stimulated Akt and mitogen-activated protein kinase phosphorylation. Hyperinsulinemic-euglycemic clamp studies revealed that disruption of Grb10 gene expression in peripheral tissues led to increased insulin sensitivity. Taken together, our results provide strong evidence that Grb10 is a negative regulator of insulin signaling and action in vivo. [ABSTRACT FROM AUTHOR]

Sympathetic tone and the number of beta adrenergic receptors (BARs) in liver increase with age, suggesting that increased BAR stimulation may contribute to the insulin resistance of aging. We hypothesized that pharmacologic BAR stimulation in young, awake, unrestrained rats would mimic the hepatic insulin resistance observed in aging. We performed a pancreatic clamp on 4 month old Fischer 344 male rots (n=6) by infusing somatostatin (3 µg⋅'kg-1⋅min1) at time zero to inhibit insulin secretion, and then infused insulin (1 mU⋅kg1⋅min-1) to replace basal insulin concentrations. At time zero, rats also received either the BAR agonist isoproterenol (ISO) (100 ng⋅kg-1⋅min-1) or saline. At 120 min, the insulin infusion rate was increased to 4 mU⋅kg-1⋅min-1 and 20% dextrose was infused to maintain the plasma glucose concentration at basal values for an additional 120 min. Tritiated glucose was infused throughout (0-240 min) to measure glucose turnover rates. Results: During the initial 120 min (basal plasma insulin concentrations), plasma glucose increased with ISO but remained unchanged with saline (Figure 1). Throughout the 120-240 min time-period of hyperinsulinemia, hepatic glucose production (HGP) was suppressed during saline infusion (from 8.3±0.6 to 0.±0.2 mg⋅kg-l⋅min-1), whereas insulin suppression of HGP was markedly impaired during ISO infusion (8.2±0.9 to 6.7±-0.6 mg⋅kg-1⋅min-1) (p<0.001 vs. saline; p=NS vs. baseline). The total glucose disposal rate during hyperinsulinemia was similar in the ISO and saline groups (16.7±2.0 vs 18.8±2.2 mg⋅kg-1·min-1, p=NS). Conclusions: Pharmacologic BAR stimulation increases HGP and acutely induces hepatic insulin resistance in Fischer 344 male rats, suggesting that BAR stimulation may contribute to the hepatic insulin resistance of aging. [ABSTRACT FROM AUTHOR]

Non-Alcoholic Steatohepatitis (NASH) is a chronic liver disease frequently associated with insulin resistance and type 2 diabetes mellitus (T2DM), and characterized by steatosis and necroinflammation with or without perisinusoidal fibrosis. We have recently reported that 6 months treatment with pioglitazone (PIO) reverses the metabolic and histological abnormalities of patients with IGT or T2DM and NASH, but also leads to weight gain. We performed a careful evaluation to understand the nature of weight gain associated with PIO treatment in NASH, as it may be important to establish the safety of its use in this population. To this end we analyzed a subgroup of 35 patients who completed the tests for determination of whole body fat (WBF) and total body water (TBW): 21 patients received PIO (9 IGT/12 T2DM) and 14 placebo (6 IGT/8 T2DM), in a double-blind, randomized fashion for a period of 6 months. WBF and TBW were measured before and after treatment using dual energy X-ray absorptiometry (DXA, Hologic Inc, Waltham, MA), a water dilution technique using 3H20 and bioimpedance. Results: PIO increased body weight (from 93.6±19.2 to 96.1±20.8 kg, p<0.003) and WBF as measured by DXA (from 31.8±8.3 to 33.9±9.6 kg, p<0.003) while no changes were seen with placebo. Total body water measured with 3H20 was not altered significantly either after PIO (from 45.0±10.5 to 45.3±9.6) or placebo (from 44.5±9.9 to 44.6±12.5 1), p=NS. Muscle hydration [(assessed by the ratio of TBW (measured with 3H20) over fat-free mass (measured with DXA)] was unchanged both by PIO (from 0.72±0.07 to 0.73±0.07, p=NS) and placebo treatments (from 0.75±0.06 to 0.72±0.061/kg, p=NS). Extracellular water (measured with bioimpedance) was unchanged both in PIO (from 18.2±3.5 to 18.6±3.4) and in placebo (from 19.3±3.1 to 19.6±3.31), p=NS. Conclusion: Six months of PIO treatment in patients with IGT or T2DM and NASH is associated with mild to moderate weight gain that is attributable to an increase in adipose tissue mass and not to water retention. [ABSTRACT FROM AUTHOR]

PGC-1α is a transcriptional coactivator which regulates adaptive responses to a variety of physiologic stimuli. In the liver, PGC-1α expression is induced by fasting, whereas in muscle, its expression is increased by exercise training. In the liver, PGC-1α regulates glucose production, while in muscle PGC-1α stimulates mitochondrial biogenesis. However, the role that PGC-1α plays in controlling whole-body insulin sensitivity is not clear. Our goal was to examine the role of PGC-1α on whole-body glucose homeostasis, using a novel transgenic (TG) mouse model that globally overexpresses PGC-1α within a physiologic range [∼2-fold higher than wildtype (WT)]. At 16-32 weeks of age, awake, unrestrained, chronically catheterized mice (n=5 TG and n=9 WT) received a euglycemic hyperinsulinemic (18 mU⋅kg-1⋅min-1) clamp with 3-3H-glucose. In liver from TG, PGC-1α overexpression resulted in enhanced gene expression of the gluconeogenic enzymes PEPCK, G6Pase and HNF-4α by 2.2-, 2.5-, and 1.5-fold, respectively (P<0.05). These enzyme changes in TG mice were associated with an increase in basal hepatic glucose production (41±6 vs. 31±2 mg⋅kg-1⋅min-1; P<0.05), and impaired suppression of hepatic glucose production by insulin (53±6 vs. 94±5%; P<0.05) versus WT. In muscle from TG, PGC-1α overexpression led to 43% and 133% increases in myoglobin and troponin I slow proteins (P<0.05), changes reminiscent to the fiber-type switching observed with physical training. Insulin-stimulated total body glucose disposal (which primarily reflects muscle) was increased in TG versus WT (132±7 vs. 117±4 mg⋅kg-1⋅min-1; P<0.05). Summary: overexpression of PGC-1α, within physiologic levels, produces dichotomous effects on liver and muscle insulin sensitivity. We postulate that PGC-1α acts as a fuel gauge which couples energy demands (muscle) with the corresponding fuel supply (liver). Thus, under conditions of physiologic stress (i.e. prolonged fast and physical training), increased hepatic glucose production may help to sustain increased glucose transport and utilization in peripheral (muscle) tissues. [ABSTRACT FROM AUTHOR]

Introduction: Insulin resistance and mitochondrial dysfunction are characteristic features of type 2 diabetes and obesity. Insulin resistant individuals manifest multiple disturbances in FA metabolism and have excessive lipid accumulation in insulin target tissues. However, the intracellular mechanisms linking "lipotoxicity" and insulin resistance have yet to be elucidated. Aim: To assess effect of FA metabolites (palmitoyl carnitine [PC], palmitoyl-CoA, oleoyl-CoA) on ATP synthesis, oxygen consumption, and inner mitochondrial membrane potential in mitochondria isolated from mouse and human skeletal muscle of NGT subjects. Methods: Mitochondria were isolated by differential centrifugation and: (i) ATP synthesis rate with lueiferin-luciferase ATP-monitoring reagent; (ii) oxygen consumption with Clark electrode; (iii) inner mitochondrial membrane potential with safrin O flouresent dye were measured. Results: The dose response curve relating PC cone and mitochondrial ATP synthesis was similar in man and mouse and had an inverted U-shape: PC cone from 0.5 to 2µM progressively increased ATP synthesis; at PC cone > 5µM there was dose-dependent inhibition of ATP synthesis. Furthermore, 10 µM PC inhibited mitochondrial ATP synthesis with pyruvate and succinate by ∼90%. Similar dose response relationships were obtained with palmitoyl CoA and oleoyl CoA; palmitic acid (not transported into mitochondria) had no effect on ATP synthesis. PC caused dose-dependent reduction of oxygen consumption and inner mitochondrial membrane potential. PC-inhibition of oxygen consumption was observed in presence of the mitochondrial uncoupler FCCP, suggesting a direct effect on electron (e[sup -]) transport chain. PC inhibited reduction of cytochrome C by mitochondria respiring with pyruvate (donates e[sup -] to complex I) and succinate (donates e[sup -] to complex II). Conclusion: Physiologic increase in muscle cone of FA metabolites markedly impairs mitochondrial function and provides a mechanistic link between lipotoxicity, mitochondrial dysfunction and insulin resistance. [ABSTRACT FROM AUTHOR]