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Myoglobin (Mb) is a regulator of O2 bioavailability in type I muscle and heart, at least when tissue O2 levels drop. Mb also plays a role in regulating cellular NO pools. Robust binding of long-chain fatty acids and long-chain acylcarnitines to Mb, and enhanced glucose metabolism in hearts of Mb knockout (KO) mice, suggests additional roles in muscle intermediary metabolism and fuel selection. To evaluate this hypothesis, we measured energy expenditure (EE), respiratory exchange ratio (RER), body weight gain and adiposity, glucose tolerance and insulin sensitivity in Mb knockout (Mb-/-) and wildtype (WT) mice challenged with a high fat diet (HFD, 45% of calories). In males (n=10/genotype) and females (n=9/genotype) aged 5-6, 11-12, and 17-18 wk, there were no genotype effects on RER, EE, or food intake. RER and EE during cold (10˚C, 72 h), and glucose and insulin tolerance, were not different compared to within-sex WT controls. At ~18 and ~19 wk of age, female Mb-/- adiposity was ~42-48% higher vs. WT females (p=0.1). Transcriptomics analyses (whole gastrocnemius, soleus) revealed few consistent changes, with the notable exception of a 20% drop in soleus transferrin receptor (Tfrc) mRNA. Capillarity indices were significantly increased in Mb-/-, specifically in Mb-rich soleus and deep gastrocnemius. The results indicate that Mb loss does not have a major impact on whole-body glucose homeostasis, EE, RER, or response to a cold challenge in mice. However, the greater adiposity in female Mb-/- mice indicates a sex-specific effect of Mb KO on fat storage and feed efficiency.

Despite claims of safety or harm reduction for electronic cigarettes (E-cig) use (also known as vaping), emerging evidence indicates that E-cigs are not likely safe, or necessarily safer than traditional cigarettes, when considering the user’s risk of developing vascular dysfunction/disease. E-cigs are different from regular cigarettes in that E-cig devices are highly customizable, and users can change the e-liquid composition (such as the base solution, flavors, and nicotine level). Since the effects of E-cigs on the microvascular responses in skeletal muscle are poorly understood, we used intravital microscopy with an acute (one-time 10 puff) exposure paradigm to evaluate the individual components of e-liquid on vascular tone and endothelial function in the arterioles of the gluteus maximus muscle of anesthetized C57Bl/6 mice. Consistent with the molecular responses seen with endothelial cells, we found that the peripheral vasoconstriction response was similar between mice exposed to E-cig aerosol or cigarette smoke (i.e., 3R4F reference cigarette); this response was not nicotine dependent, and endothelial cell-mediated vasodilation was not altered within this acute exposure paradigm. We also report that, regardless of the base solution component [i.e., vegetable glycerin (VG)-only or propylene glycol (PG)-only], the vasoconstriction responses were the same in mice with inhalation exposure to 3R4F cigarette smoke or E-cig aerosol. Key findings from this work reveal that some component other than nicotine, in inhaled smoke or aerosol, is responsible for triggering peripheral vasoconstriction in skeletal muscle, and that regardless of one’s preference for an E-cig base solution composition (i.e., ratio of VG-to-PG), the acute physiological response to blood vessels appears to be the same. The data suggest that vaping is not likely to be ‘safer’ than smoking towards blood vessels and can be expected to produce and/or result in the same adverse vascular health outcomes associated with smoking cigarettes.

The use of electronic cigarette (E‐cig) devices has increased over the last decade. However, little is known about the cardiovascular effects of vaping over prolonged periods of time.Preliminary data from female Sprague Dawley rats exposed to either air (n=1), nicotine‐free E‐cig vapor without nicotine (E‐cig0, n=3) or E‐cig vapor with 18 mg/ml free‐base nicotine (E‐cig18, n=1) were obtained using 75/25 VG/PG base solution with a 3rd generation tank‐style E‐cig device. Whole body exposure was performed via a dual chamber exposure system (Scireq InExpose) consisting of 20 puffs over 1‐hour each day (1 puff every 3 minutes), 5 days/week, using 5‐sec (55 ml) puffs @17.5 watts. This resulted in an average daily total particulate matter (TPM) concentration of ~120 mg/m3. Total number of particles measured in E‐cig0 and E‐cig18 chambers was 1.09 × 1010 and 2.14 × 1010, with an average daily particle exposure of 6.4 × 105 and 1.18 ×106 particles, respectively. In‐vivo aortic stiffness was assessed under anesthesia using Vevo2100 ultra‐high frequency ultrasound imaging system (VisualSonics) by measuring pulse wave velocity (PWV) in B‐mode and Doppler ultrasound of blood flow signals of the common carotid artery (between the aortic arch and the carotid bifurcation from a single, EKG‐gated, image).Exposure began at 18 weeks (4.2 months) and ended at 40 weeks (9.3 months) of age, resulting in a total exposure period of 22 weeks (5.1 months). Based on the average life expectancy of a rat (24 months) to humans (78 years), 5.1 months of exposure in rat equates ~16.5 years of vaping in humans. Following this exposure in rats, we observed that PWV was 2.94 m/s in the air (control) group, 4.87 m/s in the E‐cig0 group, and 4.45 m/s in the E‐cig18 group. The difference in PWV between air and E‐cig groups was +1.66 m/s (E‐cig0) and +1.51 m/s (E‐cig18). These preliminary data are consistent with previous findings from chronic exposure (up to 8‐months) in mice showing significant increases in PWV with E‐cig18 (+1.14 m/s) and traditional cigarette (+1.28 m/s) exposure (p<0.05).These findings suggest that chronic vaping with or without nicotine will likely illicit similar harmful effects toward arterial stiffness in rats and mice. Given that a +1.0 m/s increase in central PWV is associated with a ~15% greater risk of cardiovascular and all‐cause mortality risk in humans, the clinical implications are that chronic vaping with or without nicotine will increase arterial stiffness and associated mortality. Clinical monitoring of vascular health should be strongly encouraged in all E‐cig users.Support or Funding Information Support: WVU Cancer Institute Philip R Dino Innovative Research Grant (IMO); Transition Grant Support; Office of Research and Graduate Education (IMO), APS STRIDE Fellowship (JO); NIHGMS 5U54GM104942‐03 (PDC)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Developmental harm to offspring from maternal exposure to electronic cigarettes (E‐cig) during pregnancy is still poorly understood. Similar to cigarettes, we hypothesized the even low‐level E‐cig exposure would produce similar evidence of cerebral vascular dysfunction compared to a higher exposure dose. We examined the effects of maternal E‐cig exposure (Joyetech eGrip OLED using 5‐sec puffs @17.5 W) on cerebrovascular function in offspring (n=2–4 from each dam) from Sprague‐Dawley rat dams exposed to air (Control), E‐cig with 18 mg/ml nicotine (E‐cig18) and without nicotine (E‐cig0). Dams were exposed to low (20 puffs) or high (60 puffs) dose for 1‐hour each day, 5 days/week, starting on gestational day 2 and continued until pups were weaned. Pups themselves we never directly exposed to E‐cig aerosol. Middle cerebral arteries (MCA) were obtained from pups at 3‐months of age, isolated and positioned in a pressurized myobath, and exposed to increasing concentrations of acetylcholine (ACh; 10 ‐9 M to 10 ‐4 M), serotonin (5‐ HT;10 ‐9 M to 10 ‐4 M), and sodium nitroprusside (SNP; 10 ‐9 M to 10 ‐4 M), and in the presence or absence of Tempol (a superoxide dismutase mimetic). At the lower dose, MCA dilation to ACh was impaired by 60±1% and 50±0.1% in E‐cig0 and E‐cig18 groups, respectively, compared to controls (p<0.05). At the higher dose, MCA dilation to ACh was similarly impaired by 63±1% and 60±0.2% in E‐cig0 and E‐cig18 groups, respectively (p<0.05). Incubation with tempol reversed the cerebrovascular dysfunction seen in both E‐cig groups at both doses, suggesting the superoxide pathway is involved in the impairment observed in offspring. At both low and high doses, the vasocontrictory response to 5‐HT, and dilation response to SNP (non‐endothelial‐dependent mechanism), were similar across all groups. These data show that maternal E‐cig usage results in similar cerebrovasculature impairment with either 20 or 60 puffs/day during pregnancy and lactation in adolescent offspring with prior in utero exposure from maternal vaping at suggesting that even low‐levels of maternal E‐cig use confers significant post‐natal vascular health risks for the offspring. Support or Funding Information WVU Cancer Institute Philip R Dino Innovative Research Grant (IMO); APS STRIDE Fellowship (JO); NIHGMS 5U54GM104942‐03 (PDC)