Leon, Barbara Gisella Carranza

The role of adipose tissue (AT) inflammation in AT function in humans is unclear. We tested whether AT macrophage (ATM) content, cytokine gene expression, and senescent cell burden (markers of AT inflammation) predict AT insulin resistance measured as the insulin concentration that suppresses lipolysis by 50% (IC50). We studied 86 volunteers with normal weight or obesity at baseline and a subgroup of 25 volunteers with obesity before and after weight loss. There was a strong positive relationship between IC50 and abdominal subcutaneous and femoral fat cell size (FCS). The positive, univariate relationships between IC50 and abdominal AT inflammatory markers CD68, CD14, CD206 ATM/100 adipocytes, senescent cells, IL-6, and TNF-α mRNA were not significant after adjustment for FCS. A 10% weight loss significantly reduced IC50; however, there was no reduction in adipose ATM content, senescent cells, or cytokine gene expression. Our study suggests that commonly used markers of AT inflammation are not causally linked to AT insulin resistance, whereas FCS is a strong predictor of AT insulin resistance with respect to lipolysis.

Abstract Context The factors that determine the recycling of free fatty acids (FFA) back into different adipose tissue depots via the direct storage pathway are not completely understood. Objective To assess the interactions between adipocyte factors and plasma FFA concentrations that determine regional FFA storage rates. Design We measured direct adipose tissue FFA storage rates before and after weight loss under high FFA (intravenous somatostatin and epinephrine) and low (intravenous insulin and glucose) FFA concentrations. Setting Mayo Clinic Clinical Research Unit. Patients Sixteen premenopausal women, body mass index 30 to 37 kg/m2. Intervention Comprehensive lifestyle weight loss program. Main Outcome Measure Direct FFA storage rates in upper and lower body subcutaneous fat. Results Over the entire range of FFA and under isolated conditions of elevated FFA concentrations, the storage rates of FFA into upper and lower body subcutaneous fat per unit lipid were associated with concentrations, not adipocyte fatty acid storage factors. Under low FFA conditions, direct FFA storage rates were related to adipocyte CD36 content, not tissue level content of fatty acid storage factors. Weight loss did not change these relationships. Conclusions The regulation of direct FFA storage under low FFA concentration conditions appears to be at the level of the cell/adipocyte content of CD36, whereas under high FFA concentration conditions, direct FFA storage at the tissue level is predicted by plasma FFA concentrations, independent of adipocyte size or fatty acid storage factors. These observations offer novel insights into how adipose tissue regulates direct FFA storage in humans.

AbstractObjectiveAdipose tissue (AT) senescence is associated with AT dysfunction in rodents, but little is known about human AT senescence. The study goal was to define the distribution of senescent cells in two subcutaneous depots and understand relationships with adiposity and inflammation.MethodsSixty‐three volunteers (48 females) underwent abdominal and femoral subcutaneous fat biopsies. Fat cell size, senescent cells using senescence‐associated β‐galactosidase staining per 100 nucleated cells (percentage), and mRNA expression of four cytokines were measured.ResultsThere was a larger proportion of senescent cells in femoral than abdominal subcutaneous AT (mean difference 1.6% [95% CI: 0.98%‐2.3%], p < 0.001), and the percentage of femoral AT senescent cells was greater in women than men (median 3.9% vs. 2.1%, p < 0.01). There was a positive correlation between senescence and fat cell size in abdominal (rs = 0.44, p < 0.001) and femoral (rs = 0.35, p = 0.007) AT depots. Abdominal AT tumor necrosis factor alpha (rs = 0.49, p < 0.01) and interleukin‐1β (rs = 0.44, p = 0.01) expression was positively correlated with abdominal, but not femoral, AT senescence.ConclusionsIn human subcutaneous AT, there are more senescent cells in femoral than abdominal depots; abdominal AT senescent cells are more associated with inflammatory signals than femoral AT senescent cells.

Objectives: The objective was to assess the effect of menopausal hormonal therapy (MHT) on all-cause and cause-specific mortality. Methods: We conducted a comprehensive search of several databases (MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials and Database of Systematic Reviews, and Scopus) from inception until August 2013. We included randomized controlled trials (RCTs) of more than 6 months of duration comparing MHT with no treatment. Pairs of independent reviewers selected trials, assessed risk of bias and extracted data. We estimated risk ratios (RRs) and 95% confidence intervals (CIs) using the random-effects model. Results: We included 43 RCTs at moderate risk of bias. Meta-analysis showed no effect on mortality (RR 0.99 [95% CI, 0.94–1.05]), regardless of MHT type or history of preexisting heart disease. No association was found between MHT and cardiac death (RR 1.04 [95% CI 0.87–1.23]) or stroke (RR 1.49 [95% CI 0.95–2.31]). Estrogen plus progesterone use was associated with a likely increase in breast cancer mortality (RR 1.96 [95% CI 0.98–3.94]), whereas estrogen use was not. MHT use was not associated with mortality of other types of cancer. In 5 trials, MHT was likely started at a younger age: 2 RCTs with mean age less than 60 and 3 RCTs with MHT started less than 10 years after menopause. Meta-analysis of these 5 RCTs showed a reduction of mortality with MHT (RR 0.70 [95% CI 0.52–0.95]). Conclusion: The current evidence suggests that MHT does not affect the risk of death from all causes, cardiac death and death from stroke or cancer. These data may be used to support clinical and policy deliberations about the role of MHT in the care of symptomatic postmenopausal women.