Carroll, Chad C.

Doxorubicin (DOX) is a highly effective chemotherapy agent. Its use is hampered however owing to severe dose‐dependent cardiovascular toxicity in cancer survivors. Multiple mechanisms have been implicated in the pathogenesis of DOX cardiotoxicity, one of which involves inflammation mediated by activation of the NFκB/TLR4/COX‐2 pathway in the heart. Knowledge regarding the toxic effects of DOX‐induced inflammation in other organ systems such as the brain has not been thoroughly investigated. Therefore, we explored the inflammatory potential of DOX by assessing TLR4 and COX‐2 levels in cortex and pial arteries isolated from ovariectomized (OVX) female Sprague‐Dawley rats. We hypothesized that DOX would promote inflammation by increasing COX‐2 expression along with expression of its upstream innate immune receptor, TLR4, both of which are under the transcriptional regulation of NFκB. OVX rats were treated with three, bi‐weekly, i.p. injections of DOX (4 mg/kg; cumulative dose 12 mg/kg) or vehicle (saline) and euthanized 5 days after the last dose. Tissues were isolated, snap frozen, homogenized, and analyzed for COX‐2, TLR4 and NFκBp65 levels using standard western blotting. Although COX‐2 is typically considered an inducible enzyme, it has been shown to be expressed under basal conditions. In cortex and pial arteries from vehicle‐treated rats, measurable levels of COX‐2 and TLR4 protein were detected. However, contrary to our hypothesis, levels of COX‐2 and TLR4 were decreased following DOX. In pial arteries, DOX elicited a reduction in both the COX‐2 72 kDa band 74 kDa band with the greatest reduction observed in the 72 kDa. The 72 kDa band corresponds to the partially glycosylated inactive form of enzyme, while the 74 kDa band has been shown to represent the fully glycosylated active form. Cytosolic levels of NFκBp65 levels were detected in brain and pial vessel lysate, however levels were not altered by DOX. Similar to brain and pial arteries, basal expression of COX‐2 and TLR4 were detected in left ventricle and DOX treatment attenuated expression. In conclusion, although others have suggested the involvement of the NFκB pathway during the development and progression of DOX‐induced cardiomyopathy, our studies demonstrate a possible novel action for the anticancer agent implicating anti‐inflammatory mechanisms, particularly in female cohorts with low circulating levels of gonadal hormones. Support or Funding Information Arizona State University Intramural Funds (SA and JD), Midwestern University Intramural Funds (CC), Sarver Heart Center (RG)

ObjectiveObesity alters protein metabolism in skeletal muscle, but consistent evidence is lacking. This study compared muscle protein synthesis in adults with obesity and in lean controls in the fasted state and during an amino acid infusion.MethodsTen subjects with obesity (age: 36 ± 3 years; BMI: 34 ± 1 kg/m2) and ten controls (age: 35 ± 3 years; BMI: 23 ± 1 kg/m2) received an infusion of L‐[2,3,3,4,5,5,5,6,6,6‐2H10]leucine (0.15 μmol/kg fat‐free mass/min) to measure muscle protein synthesis after an overnight fast and during amino acid infusion.ResultsDespite greater muscle mammalian target of rapamycin phosphorylation (P ≤ 0.05), fasted‐state mixed‐muscle and mitochondrial protein synthesis were lower in subjects with obesity (P ≤ 0.05). However, the change in mixed‐muscle protein synthesis during the amino acid infusion was 2.7‐fold greater in subjects with obesity (P ≤ 0.05), accompanied by a greater change in S6 kinase‐1 phosphorylation (P ≤ 0.05). The change in mitochondrial protein synthesis did not differ between groups (P > 0.05).ConclusionsAdults with obesity have reduced muscle protein synthesis in the fasted state, but this response is compensated for by a greater change in overall muscle protein synthesis during amino acid infusion.

Insulin stimulates muscle protein synthesis when the levels of total amino acids, or at least the essential amino acids, are at or above their postabsorptive concentrations. Among the essential amino acids, branched-chain amino acids (BCAA) have the primary role in stimulating muscle protein synthesis and are commonly sought alone to stimulate muscle protein synthesis in humans. Fourteen healthy young subjects were studied before and after insulin infusion to examine whether insulin stimulates muscle protein synthesis in relation to the availability of BCAA alone. One half of the subjects were studied in the presence of postabsorptive BCAA concentrations (control) and the other half in the presence of increased plasma BCAA (BCAA). Compared with that prior to the initiation of the insulin infusion, fractional synthesis rate of muscle protein (%/h) did not change ( P > 0.05) during insulin in either the control (0.04 ± 0.01 vs 0.05 ± 0.01) or the BCAA (0.05 ± 0.02 vs. 0.05 ± 0.01) experiments. Insulin decreased ( P < 0.01) whole body phenylalanine rate of appearance (μmol·kg−1·min−1), indicating suppression of muscle proteolysis, in both the control (1.02 ± 0.04 vs 0.76 ± 0.04) and the BCAA (0.89 ± 0.07 vs 0.61 ± 0.03) experiments, but the change was not different between the two experiments ( P > 0.05). In conclusion, insulin does not stimulate muscle protein synthesis in the presence of increased circulating levels of plasma BCAA alone. Insulin's suppressive effect on proteolysis is observed independently of the levels of circulating plasma BCAA.