The role of protein-tyrosine phosphatase 1B (PTP1B) in diabetes was investigated using an antisense oligonucleotide in ob͞ob and db͞db mice. PTP1B antisense oligonucleotide treatment normalized plasma glucose levels, postprandial glucose excursion, and HbA 1C. Hyperinsulinemia was also reduced with improved insulin sensitivity. PTP1B protein and mRNA were reduced in liver and fat with no effect in skeletal muscle. Insulin signaling proteins, insulin receptor substrate 2 and phosphatidylinositol 3 (PI3)-kinase regulatory subunit p50␣, were increased and PI3-kinase p85␣ expression was decreased in liver and fat. These changes in protein expression correlated with increased insulin-stimulated protein kinase B phosphorylation. The expression of liver gluconeogenic enzymes, phosphoenolpyruvate carboxykinase, and fructose-1,6-bisphosphatase was also down-regulated. These findings suggest that PTP1B modulates insulin signaling in liver and fat, and that therapeutic modalities targeting PTP1B inhibition may have clinical benefit in type 2 diabetes.

Protein tyrosine phosphatase 1B (PTP1B) is a negative regulator of insulin receptor (IR) signal transduction and a drug target for treatment of type 2 diabetes. Using PTP1B antisense oligonucleotides (ASOs), effects of decreased PTP1B levels on insulin signaling in diabetic ob/ob mice were examined. Insulin stimulation, prior to sacrifice, resulted in no significant activation of insulin signaling pathways in livers from ob/ob mice. However, in PTP1B ASO-treated mice, in which PTP1B protein was decreased by 60% in liver, similar stimulation with insulin resulted in increased tyrosine phosphorylation of the IR and IR substrate (IRS)-1 and -2 by threefold, fourfold, and threefold, respectively. IRS-2-associated phosphatidylinositol 3-kinase activity was also increased threefold. Protein kinase B (PKB) serine phosphorylation was increased sevenfold in liver of PTP1B ASO-treated mice upon insulin stimulation, while phosphorylation of PKB substrates, glycogen synthase kinase (GSK)-3␣ and -3␤, was increased more than twofold. Peripheral insulin signaling was increased by PTP1B ASO, as evidenced by increased phosphorylation of PKB in muscle of insulin-stimulated PTP1B ASOtreated animals despite the lack of measurable effects on muscle PTP1B protein. These results indicate that reduction of PTP1B is sufficient to increase insulindependent metabolic signaling and improve insulin sensitivity in a diabetic animal model. Diabetes 52:21-28, 2003

The c-Jun N-terminal kinases (JNK-1, -2, and -3) are members of the mitogen activated protein (MAP) kinase family of enzymes. They are activated in response to certain cytokines, as well as by cellular stresses including chemotoxins, peroxides, and irradiation. They have been implicated in the pathology of a variety of different diseases with an inflammatory component including asthma, stroke, Alzheimer's disease, and type 2 diabetes mellitus. In this work, high-throughput screening identified a JNK inhibitor with an excellent kinase selectivity profile. Using X-ray crystallography and biochemical screening to guide our lead optimization, we prepared compounds with inhibitory potencies in the low-double-digit nanomolar range, activity in whole cells, and pharmacokinetics suitable for in vivo use. The new compounds were over 1,000-fold selective for JNK-1 and -2 over other MAP kinases including ERK2, p38alpha, and p38delta and showed little inhibitory activity against a panel of 74 kinases.

Protein tyrosine phosphatase 1B (PTP1B) has been implicated as a negative regulator of insulin action. Overexpression of PTP1B protein has been observed in insulin-resistant states associated with obesity. Mice lacking a functional PTP1B gene exhibit increased insulin sensitivity and are resistant to weight gain. To investigate the role of PTP1B in adipose tissue from obese animals, hyperglycemic obese (ob/ob) mice were treated with PTP1B antisense oligonucleotide (ISIS-113715). A significant reduction in adiposity correlated with a decrease of PTP1B protein levels in fat. Antisense treatment also influenced the triglyceride content in adipocytes, correlating with a downregulation of genes encoding proteins involved in lipogenesis, such as sterol regulatory element-binding protein 1 and their downstream targets spot14 and fatty acid synthase, as well as other adipogenic genes, lipoprotein lipase, and peroxisome proliferator-activated receptor ␥. In addition, an increase in insulin receptor substrate-2 protein and a differential regulation of the phosphatidylinositol 3-kinase regulatory subunit (p85␣) isoforms expression were found in fat from antisense-treated animals, although increased insulin sensitivity measured by protein kinase B phosphorylation was not observed. These results demonstrate that PTP1B antisense treatment can modulate fat storage and lipogenesis in adipose tissue and might implicate PTP1B in the enlargement of adipocyte energy stores and development of obesity. Diabetes 51:2405-2411, 2002 P rotein tyrosine phosphatases play an important role in the regulation of insulin signal transduction, and a number of protein tyrosine phosphatases have been reported to regulate insulin receptor (IR) signaling both under normal conditions and in the insulin-resistant state (1-3). PTP1B has been shown to serve as a negative regulator of IR and IR substrate (IRS)-1 phosphorylation (4,5). In addition, several studies have demonstrated that increased expression of PTP1B occurs in insulin-resistant states associated with obesity (6,7). Mice lacking a functional PTP1B gene exhibit increased insulin sensitivity in liver and skeletal muscle but fail to show increased insulin sensitivity in fat. They are resistant to weight gain on a high-fat diet (8) and are reported to have low adiposity due to a marked reduction in fat cell mass without a decrease in adipocyte number (9). The reason for the obesity resistance observed in PTP1BϪ/Ϫ mice is unclear. Increased leptin sensitivity in PTP1BϪ/Ϫ mice has been suggested as a mechanism for increased energy expenditure (9). Although these reports demonstrate a major role of PTP1B in the modulation of insulin sensitivity in liver and muscle, they fail to address the effect of reducing PTP1B expression in adipose tissue in obese diabetic animals.Recently, we have investigated the effects of PTP1B antisense (ISIS-113715) treatment on insulin resistance and the regulation of insulin signaling in ob/ob diabetic mice. Interestingly, hyperglycemic ob/ob mice as well as db/db mice...