Type 2 diabetes mellitus (T2DM) is associated with increased total plasma free fatty acid (FFA) concentrations and an elevated risk of cardiovascular disease. The exact mechanisms by which the plasma FFA profile of subjects with T2DM changes is unclear, but it is thought that dietary fats and changes to lipid metabolism are likely to contribute. Therefore, establishing the changes in concentrations of specific FFAs in an individual’s plasma is important. Each type of FFA has different effects on physiological processes, including the regulation of lipolysis and lipogenesis in adipose tissue, inflammation, endocrine signalling and the composition and properties of cellular membranes. Alterations in such processes due to altered plasma FFA concentrations/profiles can potentially result in the development of insulin resistance and coagulatory defects. Finally, fibrates and statins, lipid-regulating drugs prescribed to subjects with T2DM, are also thought to exert part of their beneficial effects by impacting on plasma FFA concentrations. Thus, it is also interesting to consider their effects on the concentration of FFAs in plasma. Collectively, we review how FFAs are altered in T2DM and explore the likely downstream physiological and pathological implications of such changes.

Although details of the molecular mechanisms for the uptake of the essential nutrient zinc into the bloodstream and its subsequent delivery to zinc-requiring organs and cells are poorly understood, it is clear that in vertebrates the majority of plasma zinc (9–14 μM; approx. 75–85%) is bound to serum albumin, constituting part of the so-called exchangeable pool. The binding of metal ions to serum albumins has been the subject of decades of studies, employing a multitude of techniques, but only recently has the identity and putative structure of the major zinc site on albumin been reported. Intriguingly, this site is located at the interface between two domains, and involves two residues from each of domains I and II. Comparisons of X-ray crystal structures of free and fatty-acid bound human serum albumin suggest that zinc binding to this site and fatty acid binding to one of the five major sites may be interdependent. Interactive binding of zinc and long-chain fatty acids to albumin may therefore have physiological implications.

Covering: 1999 to 2009 Metallothioneins have been the subject of intense study for five decades, and have greatly inspired the development of bio-analytical methodologies including multi-dimensional and multi-nuclear NMR. With further advancements in molecular biology, protein science, and instrumental techniques, recent years have seen a renaissance of research into metallothioneins. The current report focuses on in vitro studies of so-called class II metallothioneins from a variety of phyla, highlighting the diversity of metallothioneins in terms of structure, biological functions, and molecular functions such as metal ion specificity, thermodynamic stabilities, and kinetic reactivity. We are still far from being able to predict any of these properties, and further efforts will be required to generate the knowledge that will enable a better understanding of what governs the biological and chemical properties of these unusual and intriguing small proteins.

Albumin is the major transport protein in blood for Zn ²⁺ , a metal ion required for physiological processes and recruited by various drugs and toxins. However, the Zn ²⁺ -binding site(s) on albumin is ill-defined. We have analyzed the 18 x-ray crystal structures of human albumin in the PDB and identified a potential five-coordinate Zn site at the interface of domains I and II consisting of N ligands from His-67 and His-247 and O ligands from Asn-99, Asp-249, and H ₂ O, which are the same amino acid ligands as those in the zinc enzymes calcineurin, endonucleotidase, and purple acid phosphatase. The site is preformed in unliganded apo-albumin and highly conserved in mammalian albumins. We have used ¹¹¹ Cd NMR as a probe for Zn ²⁺ binding to recombinant human albumin. We show that His-67 → Ala (His67Ala) mutation strongly perturbs Cd ²⁺ binding, whereas the mutations Cys34Ala, or His39Leu and Tyr84Phe (residues which may H-bond to Cys-34) have no effect. Weak Cl ⁻ binding to the fifth coordination site of Cd ²⁺ was demonstrated. Cd ²⁺ binding was dramatically affected by high fatty acid loading of albumin. Analysis of the x-ray structures suggests that fatty acid binding to site 2 triggers a spring-lock mechanism, which disengages the upper (His-67/Asn-99) and lower (His-247/Asp-249) halves of the metal site. These findings provide a possible mechanism whereby fatty acids (and perhaps other small molecules) could influence the transport and delivery of zinc in blood.

Most blood plasma zinc is bound to albumin, but the structure of the binding site has not been determined. Zn K-edge extended x-ray absorption fine structure spectroscopy and modeling studies show that the major Zn²⁺ site on albumin is a 5-coordinate site with average Zn-O/N distances of 1.98 Å and a weak sixth O/N bond of 2.48 Å, consistent with coordination to His⁶⁷ and Asn⁹⁹ from domain I, His²⁴⁷ and Asp²⁴⁹ from domain II (residues conserved in all sequenced mammalian albumins), plus a water ligand. The dynamics of the domain I/II interface, thought to be important to biological function, are affected by Zn²⁺ binding, which induces cooperative allosteric effects related to those of the pH-dependent neutral-to-base transition. N99D and N99H mutations enhance Zn²⁺ binding but alter protein stability, whereas mutation of His⁶⁷ to alanine removes an interdomain H-bond and weakens Zn²⁺ binding. Both wild-type and mutant albumins promote the safe management of high micromolar zinc concentrations for cells in cultures.