Effects of 3T3 adipocytes on interleukin-6 expression and insulin signaling in L6 skeletal muscle cells.

OBJECTIVE: Central adiposity and inflammation play key roles in the development of insulin resistance through the effects of pro-inflammatory adipokines such as IL-6, but the effect of infiltrating adipocytes in skeletal muscle tissues is not known. Communications between muscle cells and fat cells may contribute to the inflammatory response associated with insulin resistance. METHODS: In this study we used a co-culture system of skeletal muscle (L6) and adipocyte (3T3-L1) cell lines to study expression of the inflammatory cytokine IL-6 and changes in insulin signaling. This model could mimic the adipocytes infiltrating myocytes that is commonly seen in obese patients. RESULTS: When plated alone the L6 cells express IL-6 mRNA and secrete IL-6 protein, both of which are increased when the cells are challenged with the bacterial lipopolysaccharide (LPS). In contrast, the 3T3-L1 cells had very little expression of IL-6 mRNA or protein. Co-culture of 3T3-L1 pre-adipocytes with L6 cells, at a density ratio of 1:10, respectively, increased IL-6 expression significantly and decreased insulin-stimulated Akt phosphorylation. To examine the role of IL-6 in insulin sensitivity we incubated the L6 cells with IL-6. A brief challenge of L6 cells with IL-6 enhanced insulin-stimulated Akt phosphorylation. In contrast, incubation of the L6 cells with IL-6 for 96h markedly decreased insulin-stimulated Akt phosphorylation. CONCLUSION: The enhanced IL-6 mRNA expression and IL-6 release in L6 myocytes co-cultured with 3T3-L1 cells indicate an important interaction between adipocytes and myocytes. This observation may shed some light on the long-standing enigma of obesity-induced insulin resistance where infiltration of the skeletal muscle by preadipocytes/adipocytes is evident.

[Oculocutaneous albinism in French overseas territories (Reunion, French Guyana, Martinique) and Mayotte. Study of 21 cases in 16 families]. / L'albinisme oculocutané dans les départements français d'Outre-Mer (Réunion, Guyane, Martinique) et à Mayotte: à propos de 21 observations dans 16 familles.

The dual purpose of this study was to determine the genotype of patients with oculocutaneous albinism type 1 and 2 based on analysis of tyrosinase and P gene mutations and to attempt to establish a correlation between phenotype and genotype. This study included a total of 21 Caucasian, Indian and Black African patients from La Reunion, la Martinique, French Guyana and Mayotte. PCR-sequencing of genomic DNA was performed to detect tyrosinase gene mutations and PCR-separation of PCR products by agarose gel electrophoresis was performed to detect 2.7kb deletion allele of the P gene. Tyrosinase gene mutations were identified in two cases, i.e., on eheterozygous guanine "g" deletion (c.572 delG) with a frameshift (Gly191fs) resulting in apremature termination signal at codon 225 in a Caucasian patient from La Reunion and one homozygous missense mutation, Glycine419Arginine, in an Indian patient from La Reunion. The 2.7-kb deletion allele of the P gene was detected in three Black African patients, i.e. two in the homozygous state in siblings from Mayotte and one in the heterozygous state in a girl from la Martinique. The latter patient whose mother was from la Martinique inherited the mutation from her father who was from Cameroon. This study shows that characterization of tyrosinase and P gene mutations in albinos patients is crucial to (a) differentiate subjects with oculocutaneous albinism types 1 and 2 and establish a correlation between phenotype and genotype, (b) identify healthy heterozygous carriers among the patient's immediate family (parents and siblings) and (c) allow prenatal diagnosis during subsequent pregnancies in couples who have already engendered albino children with severe visual phenotype and documented mutation(s).

Identification and quantitation of mucosal and faecal desulfovibrios using real time polymerase chain reaction.

BACKGROUND: Desulfovibrios produce sulphide, which is toxic to colonic epithelial cells. These bacteria have previously been linked to ulcerative colitis. Traditional methods of culturing these organisms are slow, and often unreliable, while molecular approaches are either non-quantitative or lack sensitivity. AIMS: To develop a sensitive method for quantitating desulfovibrios in stools and biopsy tissue, and to investigate the effects of age and disease on these bacteria. METHODS: Rectal biopsies were taken from 10 colitis patients and 10 healthy controls. Stool samples were obtained from 10 healthy infants (mean age 1.01 (0.18) years), 10 healthy young adults (26.7 (1.2) years), and 10 healthy elderly people (71.7 (1.2) years). Primers were designed and developed for analysing Desulfovibrio populations in the bowel using real time polymerase chain reaction (PCR). RESULTS: The PCR primers were highly specific for desulfovibrios. Large numbers (approximately 10(6)-10(7)/g) occurred in biopsies in colitis patients and healthy subjects, and no disease related differences were observed. Measurements of mucosal desulfovibrios over 12 months showed marked changes in some patients. Infants (10(6)-10(7)/g) and elderly people (10(7)-10(8)/g) had significantly higher numbers of desulfovibrios in stools compared with young adults (10(5)/g). CONCLUSIONS: Real time PCR analysis of desulfovibrios was an efficient and accurate method for studying these potentially harmful microorganisms. Desulfovibrios were ubiquitous in the bowel, irrespective of age. As rectal mucosae were heavily colonised in health and disease, if these bacteria play a role in colitis, some host defect, possibly in sulphide detoxication pathways or in bacterial antigen handling, is required for manifestations of pathogenicity.