Exploring the Interplay between Diabetes and Lp(a): Implications for Cardiovascular Risk.

PURPOSE OF REVIEW: The objective of this manuscript is to review and describe the relationship between Lp(a) and diabetes, exploring both their association and synergy as cardiovascular risk factors, while also describing the current evidence regarding the potential connection between low levels of Lp(a) and the presence of diabetes. RECENT FINDINGS: Epidemiological studies suggest a potential relationship between low to very low levels of Lp(a) and diabetes. Lipoprotein(a), or Lp(a), is an intriguing lipoprotein of genetic origin, yet its biological function remains unknown. Elevated levels of Lp(a) are associated with an increased risk of cardiovascular atherosclerosis, and coexisting diabetes status confers an even higher risk. On the other hand, epidemiological and genetic studies have paradoxically suggested a potential relationship between low to very low levels of Lp(a) and diabetes. While new pharmacological strategies are being developed to reduce Lp(a) levels, the dual aspects of this lipoprotein's behavior need to be elucidated in the near future.

Influence of humidity and iron(iii) on photodegradation of atmospheric secondary organic aerosol particles.

The absorption of solar actinic radiation by atmospheric secondary organic aerosol (SOA) particles drives condensed-phase photochemical processes, which lead to particle mass loss by the production of CO, CO2, hydrocarbons, and various oxygenated volatile organic compounds (OVOCs). We examined the influence of relative humidity (RH) and Fe(iii) content on the OVOC release and subsequent mass loss from secondary organic aerosol material (SOM) during UV irradiation. The samples were generated in a flow tube reactor from the oxidation of d-limonene by ozone. The SOM was collected with a Micro Orifice Uniform Deposit Impactor (MOUDI) on CaF2 windows. To selected samples, a variable amount of FeCl3 was added before irradiation. The resulting SOM samples, with or without added FeCl3, were irradiated with a 305 nm light-emitting diode and the release of several OVOCs, including acetic acid, acetone, formic acid and acetaldehyde, was measured with a Proton Transfer Reaction Time-of-Flight Mass Spectrometer (PTR-ToF-MS). The release of OVOCs from photodegradation of SOM at typical ambient mid-values of RH (30-70%) was 2-4 times higher than under dry conditions. The release of OVOCs was slightly enhanced in the presence of low concentrations of iron (0.04 Fe molar ratio) but it was suppressed at higher concentrations (0.50 Fe molar ratio) of iron indicating the existence of a complicated radical chemistry driving the photodegradation of SOM. Our findings suggest that the presence of iron in atmospheric aerosol particles will either increase or decrease release of OVOCs due to the photodegradation of SOM depending on whether the relative iron concentration is low or high, respectively. At atmospherically relevant RH conditions, the expected fractional mass loss induced by these photochemical processes from limonene SOA particles would be between 2 and 4% of particle mass per hour. Therefore, photodegradation is an important aging mechanism for this type of SOA.

Aging induced changes in ice nucleation activity of combustion aerosol as determined by near edge X-ray absorption fine structure (NEXAFS) spectroscopy.

Fresh soot particles are generally hydrophobic, however, particle hydrophilicity can be increased through atmospheric aging processes. At present little is known on how particle chemical composition and hydrophilicity change upon atmospheric aging and associated uncertainties governing the ice cloud formation potential of soot. Here we sampled two propane flame soots referred to as brown and black soot, characterized as organic carbon rich and poor, respectively. We investigated how the ice nucleation activity of these particles changed through aging in water and aqueous acidic solutions, using a continuous flow diffusion chamber operated at cirrus cloud temperatures (T ≤ 233 K). Single aggregates of both unaged and aged soot were chemically characterized by scanning transmission X-ray microscopy and near edge X-ray absorption fine structure (STXM/NEXAFS) measurements. Particle wettability was determined through water sorption measurements. Unaged black and brown soot particles exhibited significantly different ice nucleation activities. Our experiments revealed significantly enhanced ice nucleation activity of the aged soot particles compared to the fresh samples, lowering the required relative humidities at which ice formation can take place at T = 218 K by up to 15% with respect to water (ΔRHi ≈ 25%). We observed an enhanced water uptake capacity for the aged compared to the unaged samples, which was more pronounced for the black soot. From these measurements we concluded that there is a change in ice nucleation mechanism when aging brown soot. Comparison of the NEXAFS spectra of unaged soot samples revealed a unique spectral feature around 287.5 eV in the case of black soot that was absent for the brown soot, indicative of carbon with hydroxyl functionalities. Comparison of the NEXAFS spectra of unaged and aged soot particles indicates changes in organic functional groups, and the aged spectra were found to be largely similar across soot types, with the exception of the water aged brown soot. Overall, we conclude that atmospheric aging is important to representatively assess the ice cloud formation activity of soot particles.