L.L. Tatpati

Effect of testosterone on insulin stimulated IRS1 Ser phosphorylation in primary rat myotubes--a potential model for PCOS-related insulin resistance.

Background Polycystic ovary syndrome (PCOS) is characterized by a hyperandrogenic state and frequently develops skeletal muscle insulin resistance. We determined whether testosterone adversely affects insulin action by increasing serine phosphorylation of IRS-1636/639 in differentiated rat skeletal muscle myotubes. The phosphorylation of Akt, mTOR, and S6K, downstream targets of the PI3-kinase-IRS-1 complex were also studied. Methods Primary differentiated rat skeletal muscle myotubes were subjected to insulin for 30 min after 16-hour pre-exposure to either low (20 ng/ml) or high (200 ng/ml) doses of testosterone. Protein phosphorylation of IRS-1 Ser636/639, Akt Ser473, mTOR-Ser2448, and S6K-Thr389 were measured by Western blot with signal intensity measured by immunofluorescence. Results Cells exposed to 100 nM of insulin had increased IRS-1 Ser636/639 and Akt Ser473 phosphorylation. Cells pre-exposed to low-dose testosterone had significantly increased insulin-induced mTOR-Ser2448 and S6K-Thr389 phosphorylation (p<0.05), and further increased insulin-induced IRS-1 Ser636/639 phosphorylation (p = 0.042) compared to control cells. High-dose testosterone pre-exposure attenuated the insulin-induced mTOR-Ser2448 and S6K-Thr389 phosphorylation. Conclusions The data demonstrated an interaction between testosterone and insulin on phosphorylation of intracellular signaling proteins, and suggests a link between a hyperandrogenic, hyperinsulinemic environment and the development of insulin resistance involving serine phosphorylation of IRS-1 Ser636/639. These results may guide further investigations of potential mechanisms of PCOS-related insulin resistance.

Ovarian hyperstimulation syndrome: steps to maximize success and minimize effect for assisted reproductive outcome

OBJECTIVE To investigate the strategies used to decrease the risk of ovarian hyperstimulation syndrome (OHSS) and their impact on pregnancy and live birth rates. DESIGN Retrospective cohort analysis. SETTING University hospital. PATIENT(S) One hundred eighty-eight patients undergoing fresh in vitro fertilization (IVF) cycles between 2000 and 2004, with peak serum estradiol levels >2500 pg/mL and presumed to be at risk for OHSS. INTERVENTION(S) Coasting and elective embryo cryopreservation were evaluated for their effect on OHSS and live birth rates. MAIN OUTCOME MEASURE(S) Pregnancy, live birth rates, and OHSS incidence. RESULT(S) Out of 188 patients at risk for OHSS, 21 patients had their cycles coasted (group 1), and elective embryo cryopreservation was performed in 32 patients (group 2). In 135 patients with no other risk factors, ovulation was triggered with human chorionic gonadotropin and embryo transfer was performed (group 3). The incidence in our IVF population was 38 out of 1002 (3.8%). The overall incidence of OHSS for those who had an estradiol level >2500 pg/mL was 20.2% (38 out of 188), and none of the patients in group 1 developed OHSS; 13 out of 32 patients in group 2 (40.6%) and 25 out of 135 (18.5%) patients in group 3 developed OHSS. The live birth rate was 38%, 40%, and 45% in groups 1, 2, and 3, respectively, and the cumulative live birth rate was 52%, 75%, and 59%, respectively. CONCLUSION(S) Elective cryopreservation of embryos with subsequent frozen embryo transfer and coasting are effective ways of maximizing pregnancy and limiting severe OHSS.

Effect of Insulin Sensitizer Therapy on Amino Acids and Their Metabolites

AIMS Prior studies have reported that elevated concentrations of several plasma amino acids (AA), particularly branched chain (BCAA) and aromatic AA predict the onset of type 2 diabetes. We sought to test the hypothesis that circulating BCAA, aromatic AA and related AA metabolites decline in response to the use of insulin sensitizing agents in overweight/obese adults with impaired fasting glucose or untreated diabetes. METHODS We performed a secondary analysis of a randomized, double-blind, placebo, controlled study conducted in twenty five overweight/obese (BMI ~30kg/m(2)) adults with impaired fasting glucose or untreated diabetes. Participants were randomized to three months of pioglitazone (45mg per day) plus metformin (1000mg twice per day, N=12 participants) or placebo (N=13). We measured insulin sensitivity by the euglycemic-hyperinsulinemic clamp and fasting concentrations of AA and AA metabolites using ultra-pressure liquid chromatography tandem mass spectrometry before and after the three-month intervention. RESULTS Insulin sensitizer therapy that significantly enhanced insulin sensitivity reduced 9 out of 33 AA and AA metabolites measured compared to placebo treatment. Moreover, insulin sensitizer therapy significantly reduced three functionally clustered AA and metabolite pairs: i) phenylalanine/tyrosine, ii) citrulline/arginine, and iii) lysine/α-aminoadipic acid. CONCLUSIONS Reductions in plasma concentrations of several AA and AA metabolites in response to three months of insulin sensitizer therapy support the concept that reduced insulin sensitivity alters AA and AA metabolites.

The effect of branched chain amino acids on skeletal muscle mitochondrial function in young and elderly adults.

CONTEXT A reduction in maximal mitochondrial ATP production rate (MAPR) and mitochondrial DNA (mtDNA) abundance occurs with age in association with muscle weakness and reduced endurance in elderly people. Branched chain amino acids (BCAA) have been extensively used to improve physical performance. OBJECTIVE The objective was to determine whether an 8-h infusion of BCAA enhances MAPR equally in healthy young and elderly adults. METHODS Using a crossover study design, we compared the effect BCAA vs. saline infusion in 12 young (23.0 +/- 0.8 yr) and 12 elderly (70.7 +/- 1.1 yr) participants matched for sex and body mass index. Skeletal muscle MAPR and mtDNA abundance were measured in muscle biopsy samples obtained before and at the end of the 8-h infusion. RESULTS In young participants, MAPR with the substrates glutamate plus malate (supplying electrons to complex I) and succinate plus rotenone (complex II) increased in response to BCAA infusion, relative to a decline in MAPR in response to the saline infusion. In contrast, MAPR was unaffected by BCAA infusion in the elderly participants. Moreover, mtDNA abundance was lower in the elderly compared with the young participants but was unaffected by the BCAA infusion. Insulin and C-peptide concentrations declined over time during the saline infusion, but these declines were prevented by the BCAA infusion. CONCLUSIONS BCAA increased skeletal muscle MAPR in the young participants in comparison with saline, but this effect was not seen in the elderly participants indicating, that unlike in the young, BCAA does not increase muscle mitochondrial function in the elderly.

Effect of Insulin Sensitizer Therapy on Atherothrombotic and Inflammatory Profiles Associated With Insulin Resistance

OBJECTIVE To determine whether targeted pharmacological improvement of insulin sensitivity will normalize the associated elevations of thrombotic and inflammatory cardiovascular disease (CVD) biomarkers in individuals with insulin resistance. PATIENTS AND METHODS Study 1 was a cross-sectional study of Asian Indians with and without diabetes mellitus and Northern European Americans without diabetes (n=14 each) conducted between December 11, 2003, and July 14, 2006. Study 2 was a secondary analysis of a double-blind randomized controlled study conducted between August 19, 2005, and August 24, 2010, that included 25 individuals with untreated diabetes or impaired fasting glucose who were randomized to receive placebo (n=13) or a combination of metformin, 1000 mg twice daily, and pioglitazone, 45 mg daily (n=12), for 3 months. In both studies, measurements of insulin sensitivity (euglycemic-hyperinsulinemic clamp) and plasma inflammatory and thrombotic factor concentrations were obtained on enrollment (studies 1 and 2) and after intervention (study 2). RESULTS Study 1 demonstrated significant correlations between insulin sensitivity and plasma adiponectin, high-density lipoprotein cholesterol, plasminogen activator inhibitor 1, interleukin 6, tumor necrosis factor α, and triglycerides. Insulin sensitizer therapy significantly improved insulin sensitivity, inflammatory cytokines except interleukin 6, and thrombotic factors except fibrinogen, without concomitant changes in weight, blood pressure, or body composition. CONCLUSION Insulin sensitizer therapy ameliorates inflammatory and thrombotic factors implicated in developing CVD. Interventions to improve insulin sensitivity may thus be considered as therapeutic options to reduce CVD burden in insulin-resistant states, although further research is needed to determine long-term effects on morbidity and mortality.

High Cumulative Live Births in Oocyte Donation Cycles with Cryopreservation of All Embryos

Background: Cryopreservation of all embryos in stimulated IVF cycles is occasionally necessary. Although it is known that frozen embryo transfer results in lower live birth rates per transfer, there is limited information regarding expected cumulative live birth rates for patients who are in this particular scenario. Methods: The objective was to evaluate long-term outcomes in cycles undergoing pronuclear cryopreservation of all embryos utilizing a retrospective analysis of 154 consecutive recipients from 1995 to 2006. Results: The cumulative rate of first live birth per retrieval was 66.2%, with a 36.4% live birth rate per frozen embryo transfer. Following an average 2.2 ± 0.98 transfers, 32.6% (17/52) of patients who never delivered had remaining embryos making the cumulative first live birth rate previously stated a conservative estimate. 11.7% of recipients had sibling deliveries from a single retrieval. Over 1/3 of the delivered recipients have remaining cryopreserved embryos and could pursue an additional pregnancy. Conclusion: These results suggest that pronuclear cryopreservation of all embryos in an oocyte donation cycle maintains good cumulative live birth rates, as well as chances for a sibling from a single retrieval. Recipients who must delay transfer can be reassured a high potential for live birth from their first donor retrieval.