Gene Expression in Skeletal Muscle Biopsies from People with Type 2 Diabetes and Relatives: Differential Regulation of Insulin Signaling Pathways

BACKGROUND:Gene expression alterations have previously been associated with type 2 diabetes, however whether these changes are primary causes or secondary effects of type 2 diabetes is not known. As healthy first degree relatives of people with type 2 diabetes have an increased risk of developing type 2 diabetes, they provide a good model in the search for primary causes of the disease. METHODS/PRINCIPAL FINDINGS:We determined gene expression profiles in skeletal muscle biopsies from Caucasian males with type 2 diabetes, healthy first degree relatives, and healthy controls. Gene expression was measured using Affymetrix Human Genome U133 Plus 2.0 Arrays covering the entire human genome. These arrays have not previously been used for this type of study. We show for the first time that genes involved in insulin signaling are significantly upregulated in first degree relatives and significantly downregulated in people with type 2 diabetes. On the individual gene level, 11 genes showed altered expression levels in first degree relatives compared to controls, among others KIF1B and GDF8 (myostatin). LDHB was found to have a decreased expression in both groups compared to controls. CONCLUSIONS/SIGNIFICANCE:We hypothesize that increased expression of insulin signaling molecules in first degree relatives of people with type 2 diabetes, work in concert with increased levels of insulin as a compensatory mechanism, counter-acting otherwise reduced insulin signaling activity, protecting these individuals from severe insulin resistance. This compensation is lost in people with type 2 diabetes where expression of insulin signaling molecules is reduced

Clinical classification of cancer cachexia:phenotypic correlates in human skeletal muscle

Aim – To relate muscle phenotype to a range of current diagnostic criteria for cancer cachexia Methods – 41 patients with resectable upper gastrointestinal (GI) or pancreatic cancer underwent characterisation for cachexia based on weight-loss (WL) and / or low muscularity (LM). Four diagnostic criteria were used >5%WL, >10% WL, LM, and LM + >2%WL. Patients underwent biopsy of the rectus muscle. Analysis included immunohistochemistry for fibre size and type, protein and nucleic acid concentration, and Western blots for markers of autophagy, SMAD signalling, and inflammation. Results – Compared with non-cachectic cancer patients, if patients were classified by LM or LM + >2%WL, mean muscle fibre diameter was significantly reduced (p = 0.02 and p = 0.001) repectively. No difference in fibre diameter was observed if patients were classified with WL alone. Regardless of classification, there was no difference in fibre number or proportion of fibre type across all myosin heavy chain isoforms. Mean muscle protein content was reduced and the ratio of RNA/DNA decreased if patients were classified by either >5% WL or LM + >2%WL. Compared with non-cachectic patients, when patients were classified according to >5% WL, SMAD3 protein levels were increased (p=0.022) and with >10% WL, beclin (p = 0.05) and ATG5 (p = 0.01) protein levels were also increased. There were no differences in pNFkB or pSTAT3 levels across any of the groups. Conclusions – Whereas fibre type is not targeted selectively, muscle fibre size, biochemical composition and pathway phenotype can vary according to whether the criteria for cachexia include both a measure of low muscularity and weight loss

Low prevalence of HIV Type 1 drug resistance mutations in untreated, recently infected patients from Burkina Faso, Cote d'Ivoire, Senegal, Thailand, and Vietnam : the ANRS 12134 study

The frequency of transmitted HIV drug resistance (HIVDR) was evaluated in the context of rapid scale-up of antiretroviral treatment in Thailand, Vietnam, Burkina Faso, Cote d'Ivoire, and Senegal by using an adaptation of the WHO generic protocol of the HIV Drug Resistance Threshold Survey (HIVDR-TS) for sample collection and classification. Resistance-associated mutations were interpreted using the 2009 WHO list for epidemiological surveys. We included 266 subjects from the five study sites. Of the 266 RT and PR sequences analyzed, two from Vietnam harbored virus with major drug resistance mutations (G190A in RT for one individual and M46I in PR for the second individual). Phylogenetic analysis revealed that CRF01_AE predominates (>90%) in Thailand and Vietnam. CRF02 (>65%) cocirculates with other HIV-1 variants in Senegal and Cote d'Ivoire. The prevalence of HIVDRM is scored as low (<= 5%) in all the five sites for the three drug classes analyzed. A continuous population survey for HIVDRM will provide a rational basis for maintaining or changing the current first line regimen in these countries

Gene doping: the hype and the reality

Some spectacular results from genetic manipulation of laboratory rodents and increasing developments in human gene therapy raise the spectre of genetic modification or ‘gene doping' in sports. Candidate targets include the induction of muscle hypertrophy through overexpression of specific splice variants of insulin-like growth factor-1 or blockade of the action of myostatin, increasing oxygen delivery by raising the hematocrit through the use of erythropoietin, induction of angiogenesis with vascular endothelial growth factors or related molecules and changes in muscle phenotype through expression of peroxisome-proliferator-activated receptor- delta and associated molecules. Some of these potential genetic enhancements, particularly where the genetic modification and its action are confined to the muscles, may be undetectable using current tests. This had lead to exaggerated predictions that gene doping in athletics will be common within the next few years. However, a review of the methods of gene transfer and the current ‘state of the art' in development of genetic treatments for human disease show that the prospects for gene doping remain essentially theoretical at present. Despite this conclusion, it will be important to continue to monitor improvements in the technology and to develop methods of detection, particularly those based on identifying patterns of changes in response to doping as opposed to the detection of specific agents

Comprehensive fine mapping of chr12q12-14 and follow-up replication identify activin receptor 1B (ACVR1B) as a muscle strength gene

Muscle strength is important in functional activities of daily living and the prevention of common pathologies. We describe the two-staged fine mapping of a previously identified linkage peak for knee strength on chr12q12-14. First, 209 tagSNPs in/around 74 prioritized genes were genotyped in 500 Caucasian brothers from the Leuven Genes for Muscular Strength study (LGfMS). Combined linkage and family-based association analyses identified activin receptor 1B (ACVR1B) and inhibin β C (INHBC), part of the transforming growth factor β pathway regulating myostatin – a negative regulator of muscle mass – signaling, for follow-up. Second, 33 SNPs, selected in these genes based on their likelihood to functionally affect gene expression/function, were genotyped in an extended sample of 536 LGfMS siblings. Strong associations between ACVR1B genotypes and knee muscle strength (P-values up to 0.00002) were present. Of particular interest was the association with rs2854464, located in a putative miR-24-binding site, as miR-24 was implicated in the inhibition of skeletal muscle differentiation. Rs2854464 AA individuals were ∼2% stronger than G-allele carriers. The strength increasing effect of the A-allele was also observed in an independent replication sample (n=266) selected from the Baltimore Longitudinal Study of Aging and a Flemish Policy Research Centre Sport, Physical Activity and Health study. However, no genotype-related difference in ACVR1B mRNA expression in quadriceps muscle was observed. In conclusion, we applied a two-stage fine mapping approach, and are the first to identify and partially replicate genetic variants in the ACVR1B gene that account for genetic variation in human muscle strength