Lamivudine monotherapy in children and adolescents: The devil is in the detail.

Although expanded access to antiretroviral therapy (ART), and starting lifelong ART as soon as possible after diagnosis of HIV, have dramatically improved survival and reduced morbidity in HIV-infected children and adolescents, ~20% of children will develop virological failure (VF). Children and adolescents may be at higher risk of VF and drug resistance for a number of reasons, including prevention of mother-to-child exposure, reliance on a caregiver to administer ART, poor palatability of paediatric drugs, tuberculosis/HIV co-treatment in protease inhibitor (PI) (mainly lopinavir/ritonavir)-based regimens, and adolescence being associated with poor adherence. In children with VF, if adherence issues are addressed and re-suppression is not achieved, a switch to second- or third-line drugs may be indicated, which is the gold standard in management. However, in the face of ongoing adherence challenges, with potential accumulation of resistance mutations, limited treatment options due to extensive resistance and limited approved paediatric formulations, other strategies have been used. These include continuing a failing PI regimen, switching to a holding regimen (one or more nucleoside reverse transcriptase inhibitors) or discontinuing ART. Lamivudine monotherapy is a common choice when holding regimens are used, on the premise that the lamivudine-associated M184V resistance mutation reduces viral replication and may maintain clinical and immunological stability compared with discontinuing treatment altogether. However, this strategy is generally associated with immunological, and in some cases clinical, decline after starting lamivudine monotherapy. We discuss the pros and cons of using this therapy in children. We also propose guidance for using lamivudine monotherapy, suggesting clinical and immunological criteria for its use. Close monitoring and adherence support are required with this approach. Given many new emerging ART drugs and strategies, lamivudine monotherapy should be administered temporarily, while efforts to improve adherence are implemented. It should not be considered a default option in children with VF.

AMP-activated protein kinase response to contractions and treatment with the AMPK activator AICAR in young adult and old skeletal muscle.

One characteristic of ageing skeletal muscle is a decline in mitochondrial function. Activation of AMP-activated protein kinase (AMPK) occurs in response to an increased AMP/ATP ratio, which is one potential result of mitochondrial dysfunction. We have previously observed higher AMPK activity in old (O; 30 months) vs young adult (YA; 8 months) fast-twitch muscle in response to chronic overload. Here we tested the hypothesis that AMPK would also be hyperactivated in O vs YA fast-twitch extensor digitorum longus muscles from Fischer(344) x Brown Norway (FBN) rats (n = 8 per group) in response to high-frequency electrical stimulation of the sciatic nerve (HFES) or injection of AICAR, an activator of AMPK. Muscles were harvested immediately after HFES (10 sets of six 3-s contractions, 10 s rest between contractions, 1 min rest between sets) or 1 h after AICAR injection (1 mg (g body weight)(-1) subcutaneously). The phosphorylations of AMPKalpha and acetyl-CoA carboxylase (ACC2; a downstream AMPK target) were both greatly increased (P

A role for calcium/calmodulin kinase in insulin stimulated glucose transport.

Previous research has shown that the CAMK (calcium/calmodulin dependent protein kinase) inhibitor, KN62, can lead to reductions in insulin stimulated glucose transport. Although controversial, an L-type calcium channel mechanism has also been hypothesized to be involved in insulin stimulated glucose transport. The purpose of this report was to determine if 1) L-type calcium channels and CAMK are involved in a similar signaling pathway in the control of insulin stimulated glucose transport and 2) determine if insulin induces an increase in CAMKII phosphorylation through an L-type calcium channel dependent mechanism. Insulin stimulated glucose transport was significantly (p<0.05) inhibited to a similar extent ( approximately 30%) by both KN62 and nifedipine in rat soleus and epitrochelaris muscles. The new finding of these experiments was that the combined inhibitory effect of these two compounds was not greater than the effect of either inhibitor alone. To more accurately determine the interaction between CAMK and L-type calcium channels, we measured insulin induced changes in CAMKII phosphorylation using Western blot analysis. The novel finding of this set of experiments was that insulin induced an increase in phosphorylated CAMKII ( approximately 40%) in rat soleus muscle that was reversed in the presence of KN62 but not nifedipine. Taken together these results suggest that a CAMK signaling mechanism may be involved in insulin stimulated glucose transport in skeletal muscle through an L-type calcium channel independent mechanism.

Evidence for the involvement of a phospholipase C--protein kinase C signaling pathway in insulin stimulated glucose transport in skeletal muscle.

The primary purpose of this investigation was to determine the relationship between phospholipase C (PLC) and diacylglycerol (DAG) sensitive protein kinase C isoforms in insulin signaling in skeletal muscle. Using an in vitro preparation of rat soleus muscle we found that insulin (0.6 nM) stimulated glucose transport was inhibited approximately 20 and 25% by the PKC inhibitor GF109203X and the phospholipase C inhibitor U73122 respectively (p<0.05). The combined effects of these inhibitors were no greater than the inhibitory effects of either compound alone. Western blot analysis revealed that insulin induced a redistribution of PKC beta II from the cytosol to the membrane that was reversed in the presence of GF109203X (1 microM) and U73122 (20 microM). Similarly, U73122 and GF109203X reversed the insulin induced increase in membrane associated phosphorylated (ser 660) PKC beta II. The novel finding of this investigation is that insulin induces an increase in PKC beta II translocation and phosphorylation through a U73122 sensitive pathway in quantatively the most important insulin responsive tissue, skeletal muscle. Furthermore, these results imply that PKC beta II may be one of the DAG sensitive isoforms involved in glucose transport.

The effects of phospholipase C inhibition on insulin-stimulated glucose transport in skeletal muscle.

Previous research has demonstrated that phospholipase C (PLC) is involved in insulin-stimulated glucose transport in 3T3-L1 adipocytes. The purpose of the current investigation was to determine if PLC is also involved in insulin-stimulated glucose uptake in rat skeletal muscle. To that end, we used an in vitro muscle preparation of the rat soleus muscle to test the effects of the PLC inhibitor, U73122, on glucose transport. The PLC inhibitor, U73122, led to a concentration-dependent inhibition of insulin (0.6 nmol/L)-stimulated glucose transport, whereas it had no effect on basal glucose transport. Specifically 10, 20, 50, and 150 micromol/L U73122 inhibited insulin (0.6 nmol/L)-stimulated glucose transport approximately 17%, 20%, 26%, and 38%, respectively, while an equal molar concentration of U73343 (inactive form of U73122) and/or carrier media (dimethyl sulfoxide [DMSO]) did not influence glucose uptake. A secondary aim of this investigation was to determine if increasing the concentration of insulin from a physiologic concentration (0.6 nmol/L) to a supraphysiologic concentration (6.0 nmol/L) could ameliorate the inhibitory effects of U73122. A 10-fold increase in insulin eliminated the inhibitory effects of U73122 on insulin-stimulated glucose uptake in soleus muscle. In summary, this preliminary report provides evidence to suggest that a PLC signaling mechanism modifies insulin-stimulated glucose uptake in skeletal muscle via its influence on insulin sensitivity.

Monoclonal antibody SM047 as an immunohistochemical marker of ovarian adenocarcinoma.

AIMS: This study describes the generation of a monoclonal antibody designated SM047 which binds to an epitope that is displayed by a multivalent antigen associated with the glycocalyx of ovarian adenocarcinoma cells. The study also investigates SM047 staining in adenocarcinomas of diverse sites in order to determine whether the antibody is specific for ovarian adenocarcinoma and of value in the confirmation of an ovarian origin when the site of primary tumour is unknown. METHODS AND RESULTS: SM047, an IgM monoclonal antibody, was the product of hybridoma cells derived from fusion of SP2 myeloma cells with splenocytes of a mouse that had been immunized with a membrane preparation of tumour (ovarian serous cystadenocarcinoma) and boosted with cells from a cell line established from a similar tumour in a different patient. Sixty-two primary ovarian adenocarcinomas (28 serous, 23 mucinous, five endometrioid and six clear cell), 69 adenocarcinomas arising primary at other sites and 10 mesotheliomas were stained with SM047. There was positive membrane staining, which was usually strong and widespread, in 27 of 28 ovarian serous carcinomas and in all ovarian endometrioid and clear cell carcinomas. Most ovarian mucinous tumours were negative or exhibited weak cytoplasmic staining. Staining was variable in the other tumours but there was positive staining of most endometrial, endocervical and pancreatic adenocarcinomas. Most colonic adenocarcinomas were negative or exhibited weak cytoplasmic staining. CONCLUSIONS: SM047 is strongly expressed in most ovarian serous adenocarcinomas and in other female genital tract adenocarcinomas, with the exception of ovarian mucinous tumours. The antibody may be useful in confirming the ovarian origin of an adenocarcinoma when used as part of a larger panel. This is especially so in the distinction between a non-mucinous ovarian adenocarcinoma, which usually exhibits strong membranous staining, and a colonic adenocarcinoma which is usually negative or exhibits weak cytoplasmic staining. These findings need to be confirmed by further study of larger numbers of cases.