Advances in characterization of human sirtuin isoforms: chemistries, targets and therapeutic applications

Since the discovery in 2000 that the yeast sirtuin called "Sir2" catalyzes NAD+ dependent histone deacetylation, a wave of research has focused on evaluating the biochemical and biological functions of sirtuins. Sirtuins are activated by low calorie diets in numerous organisms and are found throughout biology in species from archaea to humans. There are seven human sirtuin isoforms called SIRT1-SIRT7. The biochemical functions of SIRT1, SIRT2, SIRT3, SIRT5 and SIRT6 have been reported and NAD+ dependent deacetylase activities confirmed. In some instances the biological target substrates for each isoform have been identified, helping to connect distinct biological processes to sirtuin regulation. This knowledge has informed potential drug design strategies that target distinct sirtuin isoforms. This review presents current knowledge of biochemical activities of SIRT1-7 in humans and the biological consequences of these sirtuin activities. Regulatory principles that govern sirtuin deacetylation activity in cells are discussed as well as strategies for how sirtuins can be targeted by small molecules. Finally, this review updates research on pharmacologic sirtuin activation and allostery on sirtuins and considers new developments for detection and isolation of sirtuins in complex mixtures.

Renal dysfunction and barttin expression in Bartter syndrome Type IV associated with a G47R mutation in BSND in a family

Bartter syndrome (BS) Type IV, associated with a G47R mutation in the BSND gene, is known to result in a mild renal phenotype. However, we report here on three brothers with varying degrees of renal dysfunction from mild to end-stage renal disease associated with renal barttin and ClC-K expression. The brothers had histories of polyhydramnios, prematurity, polyuria, deafness, and small body size. Laboratory findings showed hypokalemic metabolic alkalosis, normotensive hyperreninemic hyperaldosteronism, and an increased urinary excretion of sodium, potassium and chloride, consistent with BS Type IV. Microscopic examination of renal tissue showed hyperplasia of cells at the juxtaglomerular apparatus with dilated atrophic tubules and tubulointerstitial fibrosis. A weak barttin signal related to CIC-K expression in the cytoplasm of tubule cells, but not the basement membrane, was noted. A sequence analysis of the BSND gene showed that the affected males were homozygous for a missense G47R mutation in exon 1 of BSND. These findings suggest that the G47R mutation results in a dramatic decrease in barttin expression, which appears to be related to the location of CIC-K being changed from the basement membrane to the cytoplasm in the tubule and might have varying effects on renal function associated with factors other than this gene.

A new approach for detection of leg movement using segmental electrical impedance changes

The purpose of this paper is to provide a new approach for detection using bio-impedance. This impedance is measured by the four-electrode method. As the impedance changes resulting from ankle, knee, and hip movements depend on electrode placement, we determined the optimal electrode configurations for these movements by searching for high correlation coefficients, large impedance changes, and minimum interference in ten subjects (age: 20 +/- 4). Our optimal electrode configurations showed very strong relationships between the ankle joint angle and ankle impedance (gamma = - 0.913 +/- 0.03), between the knee joint angle and knee impedance (gamma = 0.944 +/- 0.02), and between the hip joint angle and hip impedance (gamma = 0.823 +/- 0.08). This study showed that lower leg movement could be easily measured by the impedance measurement system with two pairs of skin electrodes.