The purpose of the present study was to determine the effects of prolonged hyperinsulinemia on mitochondrial respiration and uncoupling in distinct adipose tissue depots. Sixteen-week-old male mice were injected daily with placebo or insulin to induce an artificial hyperinsulinemia for 28 days. Following the treatment period, mitochondrial respiration and degree of uncoupling were determined in permeabilized perirenal, inguinal, and interscapular adipose tissue. White adipose tissue (WAT) mitochondria (inguinal and perirenal) respire at substantially lower rates compared with brown adipose tissue (BAT). Insulin treatment resulted in a significant reduction in mitochondrial respiration in inguinal WAT (iWAT) and interscapular BAT (iBAT), but not in perirenal WAT (pWAT). Furthermore, these changes were accompanied by an insulin-induced reduction in UCP-1 (uncoupling protein 1) and PGC-1α in iWAT and iBAT only, but not in pWAT or skeletal muscle. Compared with adipose tissue mitochondria in placebo conditions, adipose tissue from hyperinsulinemic mice manifested a site-specific reduction in mitochondrial respiration probably as a result of reduced uncoupling. These results may help explain weight gain so commonly seen with insulin treatment in type 2 diabetes mellitus.
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SR proteins guide the assembly of the macromolecular spliceosome for the splicing of precursor mRNA transcripts. In this issue of Biochemical Journal, Aubol et al. demonstrate that a complex of two protein kinases- SRPK1 and CLK1- can be induced in the nucleus to promote release of the SR protein SRSF1 from storage speckles, a critical step for splicing activation. The image shows the import of SRPK1 from the cytoplasm to the nucleus and the reduction of storage speckles upon the treatment of HeLa cells with the growth factor EGF.
Insulin selectively reduces mitochondrial uncoupling in brown adipose tissue in mice
Blake W. Dallon, Brian A. Parker, Aimee E. Hodson, Trevor S. Tippetts, Mitchell E. Harrison, M. Marissa A. Appiah, Jeffrey E. Witt, Jonathan L. Gibbs, Harrison M. Gray, Thomas M. Sant, Benjamin T. Bikman; Insulin selectively reduces mitochondrial uncoupling in brown adipose tissue in mice. Biochem J 14 February 2018; 475 (3): 561–569. doi: https://doi.org/10.1042/BCJ20170736
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