To determine whether the hepatic insulin resistance of obesity and type 2 diabetes is due to impaired insulininduced suppression of glycogenolysis as well as gluconeogenesis, 10 lean nondiabetic, 10 obese nondiabetic, and 11 obese type 2 diabetic subjects were studied after an overnight fast and during a hyperinsulinemic-euglycemic clamp. Gluconeogenesis and glycogenolysis were measured using the deuterated water method. Before the clamp, when glucose and insulin concentrations differed among the three groups, gluconeogenesis was higher in the diabetic than in the obese nondiabetic subjects (P < 0.05) and glycogenolysis was higher in the diabetic than in the lean nondiabetic subjects (P < 0.05). During the clamp, when glucose and insulin concentrations were matched and glucagon concentrations were suppressed, both glycogenolysis and gluconeogenesis were higher (P < 0.01) in the diabetic versus the obese and lean nondiabetic subjects. Furthermore, glycogenolysis and gluconeogenesis were higher (P < 0.01) in the obese than in the lean nondiabetic subjects. Plasma free fatty acid concentrations correlated (P < 0.001) with glucose production and gluconeogenesis both before and during the clamp and with glycogenolysis during the clamp (P < 0.01). We concluded that defects in the regulation of glycogenolysis as well as gluconeogenesis cause hepatic insulin resistance in obese nondiabetic and type 2 diabetic humans. Diabetes 54: [1942][1943][1944][1945][1946][1947][1948] 2005 T ype 2 diabetes is characterized by both fasting and postprandial hyperglycemia. Numerous studies have established that glucose production in people with type 2 diabetes is either elevated or not appropriate for the prevailing glucose and insulin concentrations (1-8). The cause(s) of these inappropriately elevated rates of glucose production remains an area of active investigation. A series of studies have shown that gluconeogenesis, whether measured with magnetic resonance spectroscopy (7) or the deuterated water method, is increased in people with type 2 diabetes (2,9 -13). On the other hand, rates of glycogenolysis have been reported to not differ in diabetic and nondiabetic individuals (2,9,10,12). However, because both hyperglycemia and hyperinsulinemia are potent inhibitors of glycogenolysis (14 -17), equal rates of glycogenolysis, despite higher glucose and insulin concentrations in diabetic subjects, imply abnormal regulation of the glycogenolytic as well as the gluconeogenic pathway.We recently confirmed this supposition (11) by demonstrating that the contribution of glycogenolysis to endogenous glucose production (henceforth referred to as glycogenolysis) was fully suppressed in nondiabetic subjects when insulin concentrations were clamped at levels slightly above basal and glucose concentrations were raised to levels typically observed in people with type 2 diabetes (i.e., ϳ11 mmol/l). In contrast, glycogenolysis persisted in people with mild (e.g., fasting glucose ϳ8 mmol/l) or severe (e.g., fasting glucose ϳ12 mmol/l) diabetes who...

To determine the mechanism(s) by which insulin inhibits endogenous glucose production (EGP) in nondiabetic humans, insulin was infused at rates of 0.25, 0.375, or 0.5 mU ⅐ kg ؊1 ⅐ min ؊1 and glucose was clamped at ϳ5.5 mmol/l. EGP, gluconeogenesis, and uridine-diphosphoglucose (UDP)-glucose flux were measured using [3-3 H]glucose, deuterated water, and the acetaminophen glucuronide methods, respectively. An increase in insulin from ϳ75 to ϳ100 to ϳ150 pmol/l (ϳ12.5 to ϳ17 to ϳ25 U/ml) resulted in progressive (ANOVA; P < 0.02) suppression of EGP (13.1 ؎ 1.3 vs. 11.7 ؎ 1.03 vs. 6.4 ؎ 2.15 mol ⅐ kg ؊1 ⅐ min ؊1 ) that was entirely due to a progressive decrease (ANOVA; P < 0.05) in the contribution of glycogenolysis to EGP (4.7 ؎ 1. The contribution of the direct (extracellular) pathway to UDP-glucose flux was minimal and constant during all insulin infusions. We conclude that higher insulin concentrations are required to suppress the contribution of gluconeogenesis of EGP than are required to suppress the contribution of glycogenolysis to EGP in healthy nondiabetic humans. Since suppression of glycogenolysis occurred without a decrease in UDP-glucose flux, this implies that insulin inhibits EGP, at least in part, by directing glucose-6-phosphate into glycogen rather than through the glucose-6-phosphatase pathway. Diabetes

OBJECTIVE-To determine mechanisms by which pioglitazone and metformin effect hepatic and extra-hepatic insulin action.RESEARCH DESIGN AND METHODS-Thirty-one subjects with type 2 diabetes were randomly assigned to pioglitazone (45 mg) or metformin (2,000 mg) for 4 months.RESULTS-Glucose was clamped before and after therapy at ϳ5 mmol/l, insulin raised to ϳ180 pmol/l, C-peptide suppressed with somatostatin, glucagon replaced at ϳ75 pg/ml, and glycerol maintained at ϳ200 mmol/l to ensure comparable and equal portal concentrations on all occasions. Insulin-induced stimulation of glucose disappearance did not differ before and after treatment with either pioglitazone (23 Ϯ 3 vs. 24 Ϯ 2 mol ⅐ kg. In contrast, pioglitazone enhanced (P Ͻ 0.01) insulin-induced suppression of both glucose production (6.0 Ϯ 1.0 vs. 0.2 Ϯ 1.6 mol ⅐ kg Ϫ1 ⅐ min Ϫ1 ) and gluconeogenesis (n ϭ 11; 4.5 Ϯ 0.9 vs. 0.8 Ϯ 1.2 mol ⅐ kg Ϫ1 ⅐ min Ϫ1 ). Metformin did not alter either suppression of glucose production (5.8 Ϯ 1.0 vs. 5.0 Ϯ 0.8 mol ⅐ kg Ϫ1 ⅐ min Ϫ1 ) or gluconeogenesis (n ϭ 9; 3.7 Ϯ 0.8 vs. 2.6 Ϯ 0.7 mol ⅐ kg Ϫ1 ⅐ min Ϫ1 ). Insulin-induced suppression of free fatty acids was greater (P Ͻ 0.05) after treatment with pioglitazone (0.14 Ϯ 0.03 vs. 0.06 Ϯ 0.01 mmol/l) but unchanged with metformin (0.12 Ϯ 0.03 vs. 0.15 Ϯ 0.07 mmol/l).CONCLUSIONS-Thus, relative to metformin, pioglitazone improves hepatic insulin action in people with type 2 diabetes, partly by enhancing insulin-induced suppression of gluconeogenesis. On the other hand, both drugs have comparable effects on insulin-induced stimulation of glucose uptake. Diabetes 57: 24-31, 2008

Previously, we demonstrated in test and validation cohorts that type I IFN (T1IFN) activity can predict non-response to tumor necrosis factor inhibitors (TNFi) in rheumatoid arthritis (RA). In this study, we examine the biology of non-classical and classical monocytes from RA patients defined by their pre-biologic treatment T1IFN activity. We compared single cell gene expression in purified classical (CL, n = 342) and non-classical (NC, n = 359) monocytes. In our previous work, RA patients who had either high IFNβ/α activity (>1.3) or undetectable T1IFN were likely to have EULAR non-response to TNFi. In this study comparisons were made among patients grouped according to their pre-biologic treatment T1IFN activity as clinically relevant: “T1IFN undetectable (T1IFN ND) or IFNβ/α >1.3” ( n = 9) and “T1IFN detectable but IFNβ/α ≤ 1.3” ( n = 6). In addition, comparisons were made among patients grouped according to their T1IFN activity itself: “T1IFN ND,” “T1IFN detected and IFNβ/α ≤ 1.3,” and “IFNβ/α >1.3.” Major differences in gene expression were apparent in principal component and unsupervised cluster analyses. CL monocytes from the T1IFN ND or IFNβ/α >1.3 group were unlikely to express JAK1 and IFI27 ( p < 0.0001 and p 0.0005, respectively). In NC monocytes from the same group, expression of IFNAR1, IRF1, TNFA, TLR4 ( p ≤ 0.0001 for each) and others was enriched. Interestingly, JAK1 expression was absent in CL and NC monocytes from nine patients. This pattern most strongly associated with the IFNβ/α>1.3 group. Differences in gene expression in monocytes among the groups suggest differential IFN pathway activation in RA patients who are either likely to respond or to have no response to TNFi. Additional transcripts enriched in NC cells of those in the T1IFN ND and IFNβ/α >1.3 groups included MYD88, CD86, IRF1, and IL8. This work could suggest key pathways active in biologically defined groups of patients, and potential therapeutic strategies for those patients unlikely to respond to TNFi.

Aims/hypothesis We sought to determine whether pioglitazone and metformin alter NEFA-induced insulin resistance in type 2 diabetes and, if so, the mechanism whereby this is effected. Methods Euglycaemic-hyperinsulinaemic clamps (glucose ∼5.3 mmol/l, insulin ∼200 pmol/l) were performed in the presence of Intralipid-heparin (IL/H) or glycerol before and after 4 months of treatment with pioglitazone (n=11) or metformin (n=9) in diabetic participants. Hormone secretion was inhibited with somatostatin in all participants. Results Pioglitazone increased insulin-stimulated glucose disappearance (p <0.01) and increased insulin-induced suppression of glucose production (p<0.01), gluconeogenesis (p<0.05) and glycogenolysis (p<0.05) during IL/H. However, glucose disappearance remained lower (p<0.05) whereas glucose production (p<0.01), gluconeogenesis (p<0.05) and glycogenolysis (p<0.05) were higher on the IL/H study day than on the glycerol study day, indicating persistence of NEFA-induced insulin resistance. Metformin increased (p<0.001) glucose disappearance during IL/H to rates present during glycerol treatment, indicating protection against NEFA-induced insulin resistance in extrahepatic tissues. However, glucose production and gluconeogenesis (but not glycogenolysis) were higher (p<0.01) during IL/H than during glycerol treatment with metformin, indicating persistence of NEFA-induced hepatic insulin resistance. Conclusions/interpretation We conclude that pioglitazone improves both the hepatic and the extrahepatic action of insulin but does not prevent NEFA-induced insulin resistance. In contrast, whereas metformin prevents NEFAinduced extrahepatic insulin resistance, it does not protect against NEFA-induced hepatic insulin resistance.