Dulaglutide decreases plasma aminotransferases in people with Type 2 diabetes in a pattern consistent with liver fat reduction: a post hoc analysis of the AWARD programme.

AIMS: To evaluate the effects of dulaglutide vs placebo on liver and glycaemic/metabolic measurements in a population with Type 2 diabetes and in a subgroup with non-alcoholic fatty liver/non-alcoholic steatohepatitis. METHODS: A total of 1499 participants from AWARD-1, AWARD-5, AWARD-8 and AWARD-9 clinical trials were included in this analysis (dulaglutide 1.5 mg, n=971 and placebo, n=528). Thresholds of alanine aminotransferase levels ≥30 IU/l in men and ≥19 IU/l in women were used to determine the subgroup who had non-alcoholic fatty liver/non-alcoholic steatohepatitis. Objectives included changes from baseline to 6 months in: (1) alanine aminotransferase, aspartate transaminase and gamma-glutamyl transpeptidase levels in the overall population and (2) alanine aminotransferase, aspartate transaminase, gamma-glutamyl transpeptidase and glycaemic/metabolic measurements (e.g. HbA1c , fasting serum glucose, body weight, lipids and homeostatic model assessment) in the non-alcoholic fatty liver/non-alcoholic steatohepatitis subgroup. RESULTS: In the overall population at 6 months, dulaglutide significantly reduced alanine aminotransferase, aspartate transaminase and gamma-glutamyl transpeptidase levels vs placebo [least squares mean treatment differences: -1.7 IU/l (95% CI -2.8, -0.6), P=0.003; -1.1 IU/l (95% CI -2.1, -0.1), P=0.037; -6.6 IU/l (95% CI -12.4, -0.8), P=0.025, respectively]. In the subgroup with non-alcoholic fatty liver/non-alcoholic steatohepatitis (alanine aminotransferase levels greater than or equal to the upper limit of normal), mean baseline liver enzyme values were 38.0 IU/l, 27.8 IU/l and 43.9 IU/l for alanine aminotransferase, aspartate transaminase and gamma-glutamyl transpeptidase, respectively. In this population, more pronounced reductions from baseline in alanine aminotransferase were observed with dulaglutide vs placebo (-8.8 IU/l vs -6.7 IU/l). In the subgroup of people with alanine aminotransferase levels less than the upper limit of normal, changes from baseline in alanine aminotransferase did not significantly differ between treatment groups (0.0 IU/l vs 0.7 IU/l). CONCLUSIONS: Once-weekly dulaglutide improved alanine aminotransferase, aspartate transaminase and gamma-glutamyl transpeptidase levels compared with placebo in a pattern consistent with liver fat reductions. Our results add further weight to the notion that glucagon-like peptide-1 receptor agonists may provide benefit in lowering liver fat in addition to their other metabolic actions.

Concentration-dependent response to pioglitazone in nonalcoholic steatohepatitis.

BACKGROUND: Pioglitazone is a safe and effective option to manage patients with type 2 diabetes and nonalcoholic steatohepatitis (NASH). However, there is marked variability in treatment response. AIM: To evaluate the relationship between concentrations of pioglitazone and its active metabolites and treatment outcomes in patients with NASH. METHODS: Pioglitazone concentrations were measured in patients with NASH treated with pioglitazone 45 mg/day for 18 months; liver biopsy samples were obtained at baseline and after treatment. The primary outcome was a ≥2-point reduction in NAFLD activity score (NAS) with at least one-point improvement in more than one liver histology category and without worsening of fibrosis. A novel marker, the pioglitazone exposure index, was calculated to consider the concentrations of pioglitazone as well as the two active metabolites. RESULTS: The response to pioglitazone was concentration-dependent as evidenced by the significant relationship between both pioglitazone concentration and pioglitazone exposure index with changes in NAS (r=.48, P=.0002 and r=.51, P<.0001, respectively), steatosis (r=.41, P=.002 and r=.46, P=.0005), and inflammation (r=.44, P=.0009 and r=.40, P=.0003). The pioglitazone exposure index was also associated with a change in ballooning (P=.04). The pioglitazone exposure index was higher in patients with NASH resolution (2.85±1.38 vs 1.78±1.48, P=.018). A predictive model for the primary outcome was developed that incorporated baseline NAS and pioglitazone exposure index (AUC=0.77). CONCLUSIONS: This study demonstrates the importance of pioglitazone exposure to variable response in patients with NASH, and indicates potential factors that may identify patients most likely to benefit from chronic pioglitazone treatment.

Structure of proof of concept studies that precede a nonalcoholic steatohepatitis development program.

Surrogate endpoints for clinical proof of concept (POC) trials in nonalcoholic steatohepatitis (NASH) are based upon expert pathological review of liver biopsies. During early development, these long-term POC studies (≥48 weeks) add cost and time to the "Go/No Go" decision process. However, it is possible to conduct short-term noninvasive POC studies utilizing biomarkers and magnetic resonance imaging. Here, we discuss the use of shorter noninvasive POC studies relative to biopsy-driven studies for drug development in NASH.

Different effects of basal insulin peglispro and insulin glargine on liver enzymes and liver fat content in patients with type 1 and type 2 diabetes.

AIMS: To compare effects of basal insulin peglispro (BIL), a hepatopreferential insulin, to insulin glargine (glargine) on aminotransferases and liver fat content (LFC) in patients with type 1 and type 2 diabetes (T1D, T2D). MATERIALS AND METHODS: Data from two Phase 2 and five Phase 3 randomized trials comparing BIL and glargine in 1709 T1D and 3662 T2D patients were integrated for analysis of liver laboratory tests. LFC, measured by magnetic resonance imaging (MRI) at baseline, 26 and 52 weeks, was analyzed in 182 T1D patients, 176 insulin-naïve T2D patients and 163 T2D patients previously treated with basal insulin. RESULTS: Alanine aminotransferase (ALT) increased in patients treated with BIL, was higher than in glargine-treated patients at 4-78 weeks (difference at 52 weeks in both T1D and T2D: 7 international units/litre (IU/L), P < .001), and decreased after discontinuation of BIL. More BIL patients had ALT ≥3× upper limit of normal (ULN) than glargine. No patient had ALT ≥3× ULN with bilirubin ≥2× ULN that was considered causally related to BIL. In insulin-naїve T2D patients, LFC decreased with glargine but was unchanged with BIL. In T1D and T2D patients previously treated with basal insulin, LFC was unchanged with glargine but increased with BIL. In all three populations, LFC was higher after treatment with BIL vs glargine (difference at 52 weeks: 2.2% to 5.3%, all P < .01). CONCLUSIONS: Compared to glargine, patients treated with BIL had higher ALT and LFC at 52-78 weeks. No severe drug-induced liver injury was apparent with BIL treatment for up to 78 weeks.

Pioglitazone in the treatment of NASH: the role of adiponectin.

BACKGROUND: Plasma adiponectin is decreased in NASH patients and the mechanism(s) for histological improvement during thiazolidinedione treatment remain(s) poorly understood. AIM: To evaluate the relationship between changes in plasma adiponectin following pioglitazone treatment and metabolic/histological improvement. METHODS: We measured in 47 NASH patients and 20 controls: (i) fasting glucose, insulin, FFA and adiponectin concentrations; (ii) hepatic fat content by magnetic resonance spectroscopy; and (iii) peripheral/hepatic insulin sensitivity (by double-tracer oral glucose tolerance test). Patients were then treated with pioglitazone (45 mg/day) or placebo and all measurements were repeated after 6 months. RESULTS: Patients with NASH had decreased plasma adiponectin levels independent of the presence of obesity. Pioglitazone increased 2.3-fold plasma adiponectin and improved insulin resistance, glucose tolerance and glucose clearance, steatosis and necroinflammation (all P < 0.01-0.001 vs. placebo). In the pioglitazone group, plasma adiponectin was significantly associated (r = 0.52, P = 0.0001) with hepatic insulin sensitivity and with the change in both variables (r = 0.44, P = 0.03). Increase in adiponectin concentration was related also to histological improvement, in particular, to hepatic steatosis (r = -0.46, P = 0006) and necroinflammation (r = -0.56, P < 0.0001) but importantly also to fibrosis (r = -0.29, P = 0.03). CONCLUSIONS: Adiponectin exerts an important metabolic role at the level of the liver, and its increase during pioglitazone treatment is critical to reverse insulin resistance and improve liver histology in NASH patients.

Reduction in hematocrit and hemoglobin following pioglitazone treatment is not hemodilutional in Type II diabetes mellitus.

Peripheral edema, mild weight gain, and anemia are often observed in type II diabetic patients treated with thiazolidinediones (TZDs). Small decreases in hemoglobin (Hb) and hematocrit (Hct) appear to be a class effect of TZDs and are generally attributed to fluid retention, although experimental data are lacking. We analyzed 50 patients with type II diabetes mellitus undergoing either placebo or pioglitazone (PIO, 45 mg/day) for 16 weeks. Before and after therapy, we measured Hb/Hct and used (3)H(2)O and bioimpedance to quantitate total body water (TBW), extracellular water, and fat-free mass. The majority (89%) of the increment in body weight was accounted for by increased body fat. Hb and Hct fell significantly in the PIO group (-0.9+/-0.2 g/dl, -2.4+/-0.5%, both P<0.0001), without change in TBW. A decline in white blood cell (-0.8+/-0.1 x 10(3)/mm(3), P<0.0001) and platelet (-15+/-6 x 10(3)/mm(3), P<0.02) counts was seen after PIO. In conclusion, the small decreases in Hb/Hct observed after 16 weeks of PIO treatment cannot be explained by an increase in TBW. Other causes, such a mild marrow suppressive effect, should be explored.

Adiponectin receptors gene expression and insulin sensitivity in non-diabetic Mexican Americans with or without a family history of Type 2 diabetes.

AIMS/HYPOTHESIS: The recent discovery of two adiponectin receptors (AdipoR1 and AdipoR2) will improve our understanding of the molecular mechanisms underlying the insulin-sensitising effect of adiponectin. The aim of this study was to determine for the first time whether skeletal muscle AdipoR1 and/or AdipoR2 gene expression levels are associated with insulin resistance. METHODS: Using RT-PCR and northern analysis we measured AdipoR1 and AdipoR2 gene expression in skeletal muscle from healthy Mexican Americans with normal glucose tolerance who had (n=8) or did not have (n=10) a family history of Type 2 diabetes. RESULTS: Gene expression profiling indicated that the AdipoR1 and AdipoR2 isoforms are highly expressed in human skeletal muscle, unlike in mice where AdipoR2 expression was highest in the liver, and AdipoR1 was highest in skeletal muscle. In the study subjects, the expression levels of AdipoR1 (p=0.004) and AdipoR2 (p=0.04), as well as plasma adiponectin concentration (p=0.03) were lower in people with a family history of Type 2 diabetes than in those with no family history of the disease. Importantly, the expression levels of both receptors correlated positively with insulin sensitivity (r=0.64, p=0.004 and r=0.47, p=0.048 respectively). CONCLUSIONS/INTERPRETATION: Collectively, these data indicate that both isoforms of the adiponectin receptor play a role in the insulin-sensitising effect of adiponectin.

Skeletal muscle insulin resistance in normoglycemic subjects with a strong family history of type 2 diabetes is associated with decreased insulin-stimulated insulin receptor substrate-1 tyrosine phosphorylation.

Normoglycemic subjects with a strong family history of type 2 diabetes are insulin resistant, but the mechanism of insulin resistance in skeletal muscle of such individuals is unknown. The present study was undertaken to determine whether abnormalities in insulin-signaling events are present in normoglycemic, nonobese subjects with a strong family history of type 2 diabetes. Hyperinsulinemic-euglycemic clamps with percutaneous muscle biopsies were performed in eight normoglycemic relatives of type 2 diabetic patients (FH(+)) and eight control subjects who had no family history of diabetes (FH(-)), with each group matched for age, sex, body composition, and ethnicity. The FH(+) group had decreased insulin-stimulated glucose disposal (6.64 +/- 0.52 vs. 8.45 +/- 0.54 mg. kg(-1) fat-free mass. min(-1); P < 0.05 vs. FH(-)). In skeletal muscle, the FH(+) and FH(-) groups had equivalent insulin stimulation of insulin receptor tyrosine phosphorylation. In contrast, the FH(+) group had decreased insulin stimulation of insulin receptor substrate (IRS)-1 tyrosine phosphorylation (0.522 +/- 0.077 vs. 1.328 +/- 0.115 density units; P < 0.01) and association of PI 3-kinase activity with IRS-1 (0.299 +/- 0.053 vs. 0.466 +/- 0.098 activity units; P < 0.05). PI 3-kinase activity was correlated with the glucose disposal rate (r = 0.567, P = 0.02). In five subjects with sufficient biopsy material for further study, phosphorylation of Akt was 0.266 +/- 0.061 vs. 0.404 +/- 0.078 density units (P < 0.10) and glycogen synthase activity was 0.31 +/- 0.06 vs. 0.50 +/- 0.12 ng. min(-1). mg(-1) (P < 0.10) for FH(+) and FH(-) subjects, respectively. Therefore, despite normal insulin receptor phosphorylation, postreceptor signaling was reduced and was correlated with glucose disposal in muscle of individuals with a strong genetic background for type 2 diabetes.

Exercise increases hexokinase II mRNA, but not activity in obesity and type 2 diabetes.

Glucose phosphorylation, catalyzed by hexokinase, is the first committed step in glucose uptake in skeletal muscle. Hexokinase II (HKII) is the isoform that is present in muscle and is regulated by insulin and muscle contraction. Glucose phosphorylation and HKII expression are both reduced in obese and type 2 diabetic subjects. A single bout of exercise increases HKII mRNA and activity in muscle from healthy subjects. The present study was performed to determine if a moderate exercise increases HKII mRNA expression and activity in patients with type 2 diabetes. Muscle biopsies were performed before and 3 hours after a single bout of cycle ergometer exercise in obese and type 2 diabetic patients. HKII mRNA and activity and glycogen synthase activity were determined in the muscle biopsies. Exercise increased HKII mRNA in obese and diabetic subjects by 1.67 +/- 0.34 and 1.87 +/- 0.26-fold, respectively (P <.05 for both). Exercise did not significantly increase HKI mRNA. When HKII mRNA increases were compared with the 2.26 +/- 0.36-fold increase in HKII mRNA previously reported for healthy lean subjects, no statistically significant differences were found. In contrast to the increase in HKII activity observed after exercise by lean healthy controls, exercise did not increase HKII activity in obese nondiabetic or diabetic subjects. Exercise increased glycogen synthase activity (GS(0.1) and GS(FV)) significantly in both obese nondiabetic and type 2 diabetic patients. The present results indicate that there is a posttranscriptional defect in the response of HKII expression to exercise in obese and type 2 diabetic subjects. This defect may contribute to reduced HKII activity and glucose uptake in these patients.

Improved glycemic control and enhanced insulin sensitivity in type 2 diabetic subjects treated with pioglitazone.

OBJECTIVE: To elucidate the effects of pioglitazone treatment on glucose and lipid metabolism in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: A total of 23 diabetic patients (age 30-70 years BMI < 36 kg/m2) who being treated with a stable dose of sulfonylurea were randomly assigned to receive either placebo (n = 11) or pioglitazone (45 mg/day) (n = 12) for 16 weeks. Before and after 16 weeks of treatment, all subjects received a 75-g oral glucose tolerance test (OGTT) and hepatic peripheral insulin sensitivity was measured with a two-step euglycemic insulin (40 and 160 mU x min(-1) x m(-2) clamp performed with 3-[3H]glucose and indirect calorimetry HbA1c measured monthly throughout the study period. RESULTS: After 16 weeks of pioglitazone treatment, the fasting plasma glucose (FPG; 184 +/- 15 to 135 +/- 11 mg/dl, P < 0.01), mean plasma glucose during OGTT(293 +/- 12 to 225 +/- 14 mg/dl, P < 0.01), and HbA1c (8.9 +/- 0.3 to 7.2 +/- 0.5%, P < 0.01 ) decreased significantly without change in fasting or glucose-stimulated insulin/C-peptide concentrations. Fasting plasma free fatty acid (FFA; 647 +/- 39 to 478 +/- 49) microEq/l, P < 0.01) and mean plasma FFA during OGTT (485 +/- 30 to 347 +/- 33 microEq/l, P < 0.01) decreased significantly after pioglitazone treatment. Before and after pioglitazone treatment, basal endogenous glucose prodution (EGP) and FPG were strongly correlated (r = 0.67, P < 0.01). EGP during the first insulin clamp step was significantly decreased after pioglitazone treatment (P < 0.05) whereas insulin-stimulated total and nonoxidative glucose disposal during the second insulin clamp was increased (P < 0.01). The change in FPG was related to the change in basal EGP, EGP during the first insulin clamp step, and total glucose disposal during the second insulin clamp step. The change in mean plasma glucose concentration during the OGGTT was strongly related to the change in total body glucose disposl during the second insulin clamp step. CONCLUSIONS: These results suggest that pioglitazone therapy in type 2 diabetic patients decreases lasting and postprandial plasma glucose levels by improving hepatic and peripheral (muscle) tissue sensitivity to insulin.

Physiological hyperinsulinemia impairs insulin-stimulated glycogen synthase activity and glycogen synthesis.

Although chronic hyperinsulinemia has been shown to induce insulin resistance, the basic cellular mechanisms responsible for this phenomenon are unknown. The present study was performed 1) to determine the time-related effect of physiological hyperinsulinemia on glycogen synthase (GS) activity, hexokinase II (HKII) activity and mRNA content, and GLUT-4 protein in muscle from healthy subjects, and 2) to relate hyperinsulinemia-induced alterations in these parameters to changes in glucose metabolism in vivo. Twenty healthy subjects had a 240-min euglycemic insulin clamp study with muscle biopsies and then received a low-dose insulin infusion for 24 (n = 6) or 72 h (n = 14) (plasma insulin concentration = 121 +/- 9 or 143 +/- 25 pmol/l, respectively). During the baseline insulin clamp, GS fractional velocity (0.075 +/- 0.008 to 0.229 +/- 0.02, P < 0.01), HKII mRNA content (0.179 +/- 0.034 to 0.354 +/- 0.087, P < 0.05), and HKII activity (2.41 +/- 0.63 to 3.35 +/- 0.54 pmol x min(-1) x ng(-1), P < 0.05), as well as whole body glucose disposal and nonoxidative glucose disposal, increased. During the insulin clamp performed after 24 and 72 h of sustained physiological hyperinsulinemia, the ability of insulin to increase muscle GS fractional velocity, total body glucose disposal, and nonoxidative glucose disposal was impaired (all P < 0.01), whereas the effect of insulin on muscle HKII mRNA, HKII activity, GLUT-4 protein content, and whole body rates of glucose oxidation and glycolysis remained unchanged. Muscle glycogen concentration did not change [116 +/- 28 vs. 126 +/- 29 micromol/kg muscle, P = nonsignificant (NS)] and was not correlated with the change in nonoxidative glucose disposal (r = 0.074, P = NS). In summary, modest chronic hyperinsulinemia may contribute directly (independent of change in muscle glycogen concentration) to the development of insulin resistance by its impact on the GS pathway.

Vanadyl sulfate improves hepatic and muscle insulin sensitivity in type 2 diabetes.

Vanadyl sulfate (VOSO(4)) is an oxidative form of vanadium that in vitro and in animal models of diabetes has been shown to reduce hyperglycemia and insulin resistance. Small clinical studies of 2- to 4-week duration in type 2 diabetes (T2DM) have led to inconsistent results. To define its efficacy and mechanism of action, 11 type 2 diabetic patients were treated with VOSO(4) at a higher dose (150 mg/day) and for a longer period of time (6 weeks) than in previous studies. Before and after treatment we measured insulin secretion during an oral glucose tolerance test, and endogenous glucose production (EGP) and whole body insulin-mediated glucose disposal using the euglycemic insulin clamp technique combined [3-(3)H]glucose infusion. Treatment significantly improved glycemic control: fasting plasma glucose (FPG) decreased from 194 +/- 16 to 155 +/- 15 mg/dL, hemoglobin A(1c) decreased from 8.1 +/- 0.4 to 7.6 +/- 0.4%, and fructosamine decreased from 348 +/- 26 to 293 +/- 12 micromol/L (all P < 0.01) without any change in body weight. Diabetics had an increased rate of EGP compared with nondiabetic controls (4.1 +/- 0.2 vs. 2.7 +/- 0.2 mg/kg lean body mass.min; P< 0.001), which was closely correlated with FPG (r = 0.56; P< 0.006). Vanadyl sulfate reduced EGP by about 20% (P< 0.01), and the decline in EGP was correlated with the reduction in FPG (r = 0.60; P< 0.05). Vanadyl sulfate also caused a modest increase in insulin-mediated glucose disposal (from 4.3 +/- 0.4 to 5.1 +/- 0.6 mg/kg lean body mass x min; P< 0.03), although the improvement in insulin sensitivity did not correlate with the decline in FPG after treatment (r = -0.16; P = NS). Vanadyl sulfate treatment lowered the plasma total cholesterol (223 +/- 14 vs. 202 +/- 16 mg/dL; P < 0.01) and low density lipoprotein cholesterol (141 +/- 14 vs. 129 +/- 14 mg/dL; P < 0.05), whereas 24-h ambulatory blood pressure was unaltered. We conclude that VOSO(4) at maximal tolerated doses for 6 weeks improves hepatic and muscle insulin sensitivity in T2DM. The glucose-lowering effect of VOSO(4) correlated well with the reduction in EGP, but not with insulin-mediated glucose disposal, suggesting that liver, rather than muscle, is the primary target of VOSO(4) action at therapeutic doses in T2DM.

Effect of rosiglitazone on glucose and non-esterified fatty acid metabolism in Type II diabetic patients.

AIMS/HYPOTHESIS: We aimed to examine the mechanisms by which rosiglitazone improves glycaemic control in Type II (non-insulin-dependent) diabetic patients. METHODS: Altogether 29 diet-treated diabetic patients were assigned at random to rosiglitazone, 8 mg/day (n = 15), or placebo (n = 14) for 12 weeks. Patients received 75 g OGTT and two-step euglycaemic insulin (40 and 160 mU/m(2)min) clamp with 3-(3)H-glucose, (14)C-palmitate and indirect calorimetry. RESULTS: After 12 weeks, rosiglitazone reduced fasting plasma glucose (195 +/- 11 to 150 +/- 7 mg/dl, p < 0.01), mean plasma glucose (PG) during OGTT (293 +/- 12 to 236 +/- 9 mg/dl, p < 0.01), and HbA1 c (8.7 +/- 0.4 to 7.4 +/- 0.3 %, p < 0.01) without changes in plasma insulin concentration. Basal endogenous glucose production (EGP) declined (3.3 +/- 0.1 to 2.9 +/- 0.1 mg/kg FFM. min, p < 0.05) and whole body glucose metabolic clearance rate increased after rosiglitazone (first clamp step: 2.8 +/- 0.2 to 3.5 +/- 0.2 ml/kg FFM. min, p < 0.01; second clamp step: 6.7 +/- 0.6 to 9.2 +/- 0.8, p < 0.05) despite increased body weight (86 +/- 4 to 90 +/- 4 kg, p < 0.01) and fat mass (33 +/- 3 to 37 +/- 3 kg, p < 0.01). Fasting plasma non-esterified fatty acid (NEFA) (735 +/- 52 to 579 +/- 49 microEq/l, p < 0.01), mean plasma NEFA during OGTT (561 +/- 33 to 424 +/- 35, p < 0.01), and basal NEFA turnover (18.3 +/- 1.5 to 15.5 +/- 1.2 microEq/kg FM. min, p < 0.05) decreased after rosiglitazone. Changes in EPG and mean plasma glucose (PG) during OGTT correlated with changes in basal EGP (r = 0.54; r = 0.58), first EGP (r = 0.36; r = 0.41), first MCR (r = -0.66; r = -0.68), second MCR (r = -0.49; r = -0.54), fasting plasma NEFA (r = 0.53; r = 0.49), and NEFA during OGTT (r = 0.66; r = 0.66). CONCLUSION/INTERPRETATION: Rosiglitazone increases hepatic and peripheral (muscle) tissue insulin sensitivity and reduces NEFA turnover despite increased total body fat mass. These results suggest that the beneficial effects of rosiglitazone on glycaemic control are mediated, in part, by the drug's effect on NEFA metabolism.

Recombinant human insulin-like growth factor I treatment for 1 week improves metabolic control in type 2 diabetes by ameliorating hepatic and muscle insulin resistance.

The administration of recombinant human insulin-like growth factor I (rhIGF-I) reduces hyperglycemia and insulin requirements in subjects with severe insulin resistance syndromes and in patients with type 2 diabetes mellitus (T2DM). However, the mechanisms responsible for the improved metabolic control are incompletely understood. One proposed mechanism is that rhIGF-I therapy in T2DM may bypass early defects in insulin action (i.e. signal transduction), leading to improved hepatic and/or peripheral insulin sensitivity. To test this hypothesis, we used the euglycemic insulin clamp to measure the response to 7 days of rhIGF-I therapy (80 microg/kg, sc, twice daily) in eight poorly controlled T2DM subjects. rhIGF-I significantly improved fasting (203 +/- 12 vs. 134 +/- 14 mg/dL; P < 0.01) and day-long (0800-1700 h; 234 +/- 11 vs. 153 +/- 10 mg/dL; P < 0.01) plasma glucose levels. Basal endogenous glucose production decreased from 3.2 +/- 0.2 to 2.7 +/- 0.2 mg/kg lean body mass x min (P < 0.03) despite a concomitant decline in the fasting plasma insulin concentration from 13 +/- 5 to 5 +/- 1 microU/mL (P < 0.01). The decrement in basal endogenous glucose production was closely correlated with the decrement in fasting plasma glucose concentration (r = 0.78; P < 0.01). Whole body insulin-stimulated glucose disposal increased by 27% (from 5.6 +/- 0.8 to 7.1 +/- 0.8 mg/kg lean body mass x min; P < 0.01), but remained well below that observed in age- and weight-matched healthy subjects. The effects of rhIGF-I on endogenous glucose production and peripheral insulin sensitivity resemble those observed with intensified insulin regimens in T2DM. We conclude that 7 days of sc rhIGF-I improves glucose control by improving hepatic and muscle insulin sensitivity, but it remains markedly abnormal. This indicates that an intrinsic defect(s) responsible for insulin resistance in T2DM cannot be overcome by rhIGF-I treatment.

Regulation of MAP kinase pathway activity in vivo in human skeletal muscle.

Insulin and exercise potently stimulate glucose metabolism and gene transcription in vivo in skeletal muscle. A single bout of exercise increases the rate of insulin-stimulated glucose uptake and metabolism in skeletal muscle in the postexercise period. The nature of the intracellular signaling mechanisms that control responses to exercise is not known. In mammalian tissues, numerous reports have established the existence of the mitogen-activated protein (MAP) kinase signaling pathway that is activated by a variety of growth factors and hormones. This study was undertaken to determine how a single bout of exercise and physiological hyperinsulinemia activate the MAP kinase pathway. The euglycemic-hyperinsulinemic clamp and cycle ergometer exercise techniques combined with percutaneous muscle biopsies were used to answer this question. In healthy subjects, within 30 min, insulin significantly increased MAP kinase [isoforms p42(MAPK) and p44(MAPK) (ERK1 and ERK2)] phosphorylation (141 +/- 2%, P < 0.05) and activity (177 +/- 5%, P < 0.05), and the activity of its upstream activator MEK1 (161 +/- 16%, P < 0.05). Insulin also increased the activity of the MAP kinase downstream substrate, the p90 ribosomal S6 kinase 2 (RSK2) almost twofold (198 +/- 45%, P < 0.05). In contrast, a single 30-min bout of moderate-intensity exercise had no effect on the MAP kinase pathway activation from MEK to RSK2 in muscle of healthy subjects. However, 60 min of exercise did increase extracellular signal-related kinase activity. Therefore, despite similar effects on glucose metabolism after 30 min, insulin and exercise regulate the MAP kinase pathway differently. Insulin more rapidly activates the MAP kinase pathway.

Insulin resistance differentially affects the PI 3-kinase- and MAP kinase-mediated signaling in human muscle.

The broad nature of insulin resistant glucose metabolism in skeletal muscle of patients with type 2 diabetes suggests a defect in the proximal part of the insulin signaling network. We sought to identify the pathways compromised in insulin resistance and to test the effect of moderate exercise on whole-body and cellular insulin action. We conducted euglycemic clamps and muscle biopsies on type 2 diabetic patients, obese nondiabetics and lean controls, with and without a single bout of exercise. Insulin stimulation of the phosphatidylinositol 3-kinase (PI 3-kinase) pathway, as measured by phosphorylation of the insulin receptor and IRS-1 and by IRS protein association with p85 and with PI 3-kinase, was dramatically reduced in obese nondiabetics and virtually absent in type 2 diabetic patients. Insulin stimulation of the MAP kinase pathway was normal in obese and diabetic subjects. Insulin stimulation of glucose-disposal correlated with association of p85 with IRS-1. Exercise 24 hours before the euglycemic clamp increased phosphorylation of insulin receptor and IRS-1 in obese and diabetic subjects but did not increase glucose uptake or PI 3-kinase association with IRS-1 upon insulin stimulation. Thus, insulin resistance differentially affects the PI 3-kinase and MAP kinase signaling pathways, and insulin-stimulated IRS-1-association with PI 3-kinase defines a key step in insulin resistance.

Thyroid function testing in psychiatric illness: Usefulness and limitations.

The assessment of thyroid function in psychiatric patients may be obscured by several effects of the psychiatric condition on both thyroid hormone and TSH levels. Acute psychiatric decompensation may result in elevation in total T(4) and free T(4) index, and less frequently in hypothyroxinemia. In addition, psychiatric illnesses can cause suppressed TSH levels, blunted TSH response to thyrotropin-releasing hormone (TRH) (particularly in depression), and elevated TSH values that may result in diagnostic errors. Even though mechanisms similar to the ones responsible for thyroid function test changes in other nonthyroidal illness could account for some of these abnormalities, other mechanisms involving dysregulation of hypothalamic-pituitary function seem to play an important role. TRH stimulation testing has also been used for the diagnosis and prognosis of some psychiatric disorders. This test, however, appears to have low sensitivity and specificity and little clinical usefulness for this purpose and may be replaced by basal TSH levels determined by highly sensitive assays. In this review, in addition to discussing the usefulness and limitations of thyroid function tests in the setting of a psychiatric condition, we provide a stepwise approach, using sensitive TSH as a first-line test in the assessment of thyroid function in psychiatric patients.

Metabolic effects of metformin on glucose and lactate metabolism in noninsulin-dependent diabetes mellitus.

Metformin is a biguanide that has been shown to effectively lower plasma glucose levels in subjects with noninsulin-dependent diabetes mellitus (NIDDM). However, its mechanism of action remains unknown. Studies that have examined the effect of metformin on hepatic glucose production (HGP) and muscle glucose utilization in NIDDM have yielded conflicting results, and little information is available about the action of metformin on lactate turnover and gluconeogenesis from lactate in humans. We studied 20 NIDDM subjects and 8 nondiabetic controls in a randomized, double blind, placebo-controlled trial to determine the effect of 15 weeks of treatment with metformin or placebo on glucose and lactate metabolism. Before and after treatment, all participants received a 7-h infusion of [6-3H]glucose and [3-14C]lactate in combination with indirect calorimetry and estimation of lactate central vein specific activity. A euglycemic insulin clamp (20 mU/m2.min) was performed during the last 3 h of the tracer infusions. The study design allowed us to evaluate the effects of metformin vs. placebo treatment on glycemic control, plasma lipid profile, HGP, insulin-mediated glucose uptake, oxidative and nonoxidative glucose metabolism, and lactate turnover. Metformin treatment significantly reduced fasting plasma glucose (196 +/- 18 vs. 152 +/- 12 mg/dL; P < 0.01), hemoglobin A1 (12.5 +/- 0.6 vs. 9.2 +/- 0.3%; P < 0.01), and plasma triglyceride and low density lipoprotein cholesterol concentrations. When diabetics were compared to nondiabetic controls, basal HGP was higher (12.9 +/- 1.0 vs. 9.8 +/- 1.2 mumol/kg.min; P < 0.01) despite the presence of fasting hyperinsulinemia and insulin-mediated total body glucose disposal (10.9 +/- 0.9 vs. 20.2 +/- 3.3 mumol/kg.min; P < 0.01) was decreased. Metformin significantly reduced fasting HGP (from 12.9 +/- 0.7 to 11.0 +/- 0.5 mumol/kg.min; P < 0.01), but did not enhance total body glucose disposal during insulin stimulation (10.9 +/- 0.9 vs. 11.0 +/- 0.5 mumol/kg.min; P = NS). Neither oxidative nor nonoxidative glucose disposal was improved by metformin treatment. The fasting plasma lactate concentration (1.1 +/- 0.1 vs. 0.6 +/- 0.1 mmol/L) and lactate turnover (14.0 +/- 0.8 vs. 10.3 +/- 0.6 mumol/kg.min) were significantly increased in diabetics and strongly correlated (r = 0.68; P < 0.001). The percent gluconeogenesis derived from lactate was similar in diabetic and control subjects (17 +/- 2% vs. 15 +/- 2%; P = NS), but the estimated rate of gluconeogenesis from lactate was increased in the diabetic group (P < 0.01). Despite the significant reduction in HGP after metformin treatment, the percentage of gluconeogenesis from lactate and the rate of lactate-derived gluconeogenesis were unchanged from baseline. Basal lactate turnover (15.4 +/- 1.4 vs. 14.8 +/- 1.4 mumol/kg.min) and lactate oxidation (7.9 +/- 0.7 vs. 8.1 +/- 0.9 mumol/ kg.min) as well as total lactate turnover and lactate oxidation during the insulin clamp were similar before and after metformin treatment. There were no changes in any of the above metabolic parameters in the placebo-treated group. In poorly controlled NIDDM subjects, the primary mechanism by which metformin improves glycemic control is related to the suppression of accelerated basal HGP, and this most likely is secondary to an inhibition of hepatic glycogenolysis. Metformin has no effect on the rate of lactate turnover or gluconeogenesis from lactate in either the basal or insulin-stimulated states.

Regulation of hexokinase II and glycogen synthase mRNA, protein, and activity in human muscle.

Insulin regulates the activity of key enzymes of glucose metabolism in skeletal muscle by altering transcription or translation or by producing activity-altering modifications of preexisting enzyme molecules. Because of the small size of percutaneous muscle biopsies, these phenomena have been difficult to study in humans. This study was performed to determine how physiological hyperinsulinemia regulates the activities of hexokinase (HK), glycogen synthase (GS), and GLUT-4 in human skeletal muscle in vivo. We determined mRNA abundance, protein content, and activities for these proteins in muscle biopsies before and after a hyperinsulinemic clamp in normal subjects. HK I, HK II, GS, and GLUT-4 were expressed in muscle. HK II accounted for 80% of total HK activity and was increased by insulin from a basal value of 2.11 +/- 0.26 to 3.35 +/- 0.47 pmol.min-1.mg protein-1 (P < 0.05); HK I activity was unaffected. Insulin increased GS activity from 3.85 +/- 0.82 to 6.06 +/- 0.49 nmol.min-1.mg-1 (P < 0.01). HK II mRNA was increased 3.3 +/- 1.3-fold (P < 0.05) by insulin infusion. HK I, GS, and GLUT-4 mRNA and protein were unaffected. Because insulin infusion increased HK II but not GS mRNA, we conclude that HK II and GS may be regulated by insulin by different mechanisms in human skeletal muscle.