Liver and Muscle in Morbid Obesity: The Interplay of Fatty Liver and Insulin Resistance

INTRODUCTION: Nonalcoholic fatty liver disease (NAFLD) can be seen as a manifestation of overnutrition. The muscle is a central player in the adaptation to energy overload, and there is an association between fatty-muscle and -liver. We aimed to correlate muscle morphology, mitochondrial function and insulin signaling with NAFLD severity in morbid obese patients. METHODS: Liver and deltoid muscle biopsies were collected during bariatric surgery in NAFLD patients. NAFLD Activity Score and Younossi's classification for nonalcoholic steatohepatitis (NASH) were applied to liver histology. Muscle evaluation included morphology studies, respiratory chain complex I to IV enzyme assays, and analysis of the insulin signaling cascade. A healthy lean control group was included for muscle morphology and mitochondrial function analyses. RESULTS: Fifty one NAFLD patients were included of whom 43% had NASH. Intramyocellular lipids (IMCL) were associated with the presence of NASH (OR 12.5, p<0.001), progressive hepatic inflammation (p = 0.029) and fibrosis severity (p = 0.010). There was a trend to an association between IMCL and decreased Akt phosphorylation (p = 0.059), despite no association with insulin resistance. In turn, hepatic steatosis (p = 0.015) and inflammation (p = 0.013) were associated with decreased Akt phosphoryation. Citrate synthase activity was lower in obese patients (p = 0.047) whereas complex I (p = 0.040) and III (p = 0.036) activities were higher, compared with controls. Finally, in obese patients, complex I activity increased with progressive steatosis (p = 0.049) and with a trend with fibrosis severity (p = 0.056). CONCLUSIONS: In morbid obese patients, presence of IMCL associates with NASH and advanced fibrosis. Muscle mitochondrial dysfunction does not appear to be a major driving force contributing to muscle fat accumulation, insulin resistance or liver disease. Importantly, insulin resistance in muscle might occur at a late point in the insulin signaling cascade and be associated with IMCL and NAFLD severity

Pemphigus autoimmunity: Hypotheses and realities

The goal of contemporary research in pemphigus vulgaris and pemphigus foliaceus is to achieve and maintain clinical remission without corticosteroids. Recent advances of knowledge on pemphigus autoimmunity scrutinize old dogmas, resolve controversies, and open novel perspectives for treatment. Elucidation of intimate mechanisms of keratinocyte detachment and death in pemphigus has challenged the monopathogenic explanation of disease immunopathology. Over 50 organ-specific and non-organ-specific antigens can be targeted by pemphigus autoimmunity, including desmosomal cadherins and other adhesion molecules, PERP cholinergic and other cell membrane (CM) receptors, and mitochondrial proteins. The initial insult is sustained by the autoantibodies to the cell membrane receptor antigens triggering the intracellular signaling by Src, epidermal growth factor receptor kinase, protein kinases A and C, phospholipase C, mTOR, p38 MAPK, JNK, other tyrosine kinases, and calmodulin that cause basal cell shrinkage and ripping desmosomes off the CM. Autoantibodies synergize with effectors of apoptotic and oncotic pathways, serine proteases, and inflammatory cytokines to overcome the natural resistance and activate the cell death program in keratinocytes. The process of keratinocyte shrinkage/detachment and death via apoptosis/oncosis has been termed apoptolysis to emphasize that it is triggered by the same signal effectors and mediated by the same cell death enzymes. The natural course of pemphigus has improved due to a substantial progress in developing of the steroid-sparing therapies combining the immunosuppressive and direct anti-acantholytic effects. Further elucidation of the molecular mechanisms mediating immune dysregulation and apoptolysis in pemphigus should improve our understanding of disease pathogenesis and facilitate development of steroid-free treatment of patients

Rare and low-frequency coding variants alter human adult height

Height is a highly heritable, classic polygenic trait with approximately 700 common associated variants identified through genome-wide association studies so far. Here, we report 83 height-associated coding variants with lower minor-allele frequencies (in the range of 0.1-4.8%) and effects of up to 2 centimetres per allele (such as those in IHH, STC2, AR and CRISPLD2), greater than ten times the average effect of common variants. In functional follow-up studies, rare height-increasing alleles of STC2 (giving an increase of 1-2 centimetres per allele) compromised proteolytic inhibition of PAPP-A and increased cleavage of IGFBP-4 in vitro, resulting in higher bioavailability of insulin-like growth factors. These 83 height-associated variants overlap genes that are mutated in monogenic growth disorders and highlight new biological candidates (such as ADAMTS3, IL11RA and NOX4) and pathways (such as proteoglycan and glycosaminoglycan synthesis) involved in growth. Our results demonstrate that sufficiently large sample sizes can uncover rare and low-frequency variants of moderate-to-large effect associated with polygenic human phenotypes, and that these variants implicate relevant genes and pathways.</p