An improved method to determine the absolute abundance of glycerol dibiphytanyl glycerol tetraether lipids

Isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs) are specific membrane lipids derived from archaea, one of the three domains of life. These lipids can be used as biomarkers in paleo-ecological studies. GDGTs can be analyzed by high performance liquid chromatography (HPLC)/mass spectrometry (MS). To quantify GDGTs, external standard curves were run monthly on the HPLC/MS. However, external standard curves represented a snapshot and do not adjust for changes during storage, dissolution and manipulation of samples or drifts in HPLC/MS conditions. To measure absolute GDGT abundances more accurately, we tested the use of a newly synthesized C46 GDGT as an internal standard. The accuracy in the determination of GDGT concentration improved significantly when using the internal standard (5% standard deviation) compared to that obtained with the monthly external standard curve (43% standard deviation). Thus, the new internal standard technique will greatly improve the accuracy of GDGT abundance measurements, increase the potential of GDGTs in paleo-ecological studies

An improved method to determine the absolute abundance of glycerol dibiphytanyl glycerol tetraether lipids

Isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs) are specific membrane lipids derived from archaea, one of the three domains of life. These lipids can be used as biomarkers in paleo-ecological studies. GDGTs can be analyzed by high performance liquid chromatography (HPLC)/mass spectrometry (MS). To quantify GDGTs, external standard curves were run monthly on the HPLC/MS. However, external standard curves represented a snapshot and do not adjust for changes during storage, dissolution and manipulation of samples or drifts in HPLC/MS conditions. To measure absolute GDGT abundances more accurately, we tested the use of a newly synthesized C46 GDGT as an internal standard. The accuracy in the determination of GDGT concentration improved significantly when using the internal standard (5% standard deviation) compared to that obtained with the monthly external standard curve (43% standard deviation). Thus, the new internal standard technique will greatly improve the accuracy of GDGT abundance measurements, increase the potential of GDGTs in paleo-ecological studies

Tenofovir Has Minimal Effect on Biomarkers of Bone Health in Youth with HIV Receiving Initial Antiretroviral Therapy

Both HIV infection and tenofovir disoproxil fumarate (TDF) treatment adversely impact bone metabolism and may lead to osteopenia, which has critical implications for youth with HIV (YWH). This study evaluates changes in the biomarkers of bone metabolism and inflammation among YWH receiving initial treatment with TDF- and non-TDF-containing antiretroviral therapies (ARTs). YWH [n = 23, median age 21 years (range 18-24), 87% male, 61% African American] were assessed for inflammatory and bone metabolism biomarkers at enrollment, after 48 weeks of TDF-containing ART, and 96 weeks of ART without TDF with continued viral suppression. Spearman's rank correlation evaluated biomarker associations. Bone alkaline phosphatase, parathyroid hormone, and osteopontin increased after TDF treatment. All fell after TDF was discontinued. Levels of RANKL and osteoprotegerin did not change throughout the study. There was little correlation between biomarkers of bone metabolism and either macrophage or lymphocyte activation at any time point. Our results establish baseline associations between bone metabolism and immune biomarkers for this population, and find that before CD4 T cell decline chronic inflammation does not perturb biomarkers of bone metabolism among YWH. The adverse effects of TDF on bone health may be marginal for YWH at the early stages of disease