Biomedical subjects

D Brisson

Publications and source records attributed to D Brisson.

5 recordsLinked to original sources

PubMed2002

Sibship stability of genotype and phenotype in myotonic dystrophy.

Myotonic dystrophy (DM1) is caused by an unstable CTG repeat expansion. Despite the evidence of birth order effect in congenital DM1, the expansion's dynamics among sibships is still unknown. The objective of this study was to determine phenotype and CTG repeat size variability in DM1 sibships, and to investigate their predictive values. We compared 86 sib pairs for CTG repeat, 61 for age at onset and 89 for DM1 phenotype. CTG repeats remained stable for 66 of the 86 sib pairs, including 25 of 27 maternal transmissions and 30 of 42 paternal transmissions. Variations of less than 10 years in the age at onset were observed in 44 of 61 sib pairs, including 16 of 18 maternal transmissions and 19 of 28 paternal transmissions. The same phenotypic severity or a variation of only one class was observed among 86 of the 89 sib pairs, including all of the 35 maternal transmissions and 30 of the 33 paternal transmissions. Birth order, intergenesic interval, oldest sib's CTG repeat or parental age and CTG repeat did not exert any significant influence. These results suggest that genotype and phenotype remained stable among sibs, although the paternal origin of the mutation seemed to reduce the predictability of the severity.

Adolescent↗

PubMed2002

The pleiotropic expression of the myotonic dystrophy protein kinase gene illustrates the complex relationships between genetic, biological and clinical covariates of male aging.

Aging is a complex process modulated by multiple interactions between environmental and genetic factors. Myotonic dystrophy (DM1) is an autosomal dominant disorder caused by an unstable (CTG)n repeat expansion in the DM1 protein kinase (DMPK) gene. The affected male patients' life expectancy at birth (53.2 years) is more than two decades below that observed in most occidental populations. The DMPK gene expression is pleiotropic and includes the premature expression of several age-related signs, symptoms and metabolic disturbances including hormonal dysfunctions, progressive decrease in muscular mass, presenile cataracts, alopecia, reduced alertness, insulin resistance, dyslipidemia, erectile dysfunction and hypogonadism. The aim of this study was to analyze the relationship between aging covariates and the severity of DM1 expression in 136 DM1 male subjects. DM1 clinical expression was assessed on a validated neuromuscular disability rating scale and was correlated with plasma total testosterone (rs = -0.31, p < 0.001), luteinizing hormone (LH) (rs = 0.52, p < 0.001) and follicle stimulating hormone (FSH) (rs = 0.54, p < 0.001) levels. Following LH releasing hormone stimulation, FSH and LH concentrations increased as a function of DM1 severity (p < 0.05). Muscular disability in DM1 was also positively associated with fasting plasma insulin and triglyceride concentrations (p < 0.05). The association of plasma apolipoprotein B and low-density lipoprotein cholesterol levels with DM1 was not linear across their distribution and tended to reflect cell membrane damage progression. These results suggest that DM1, a simple Mendelian trait, can represent a valuable model to illustrate the complex relationships between variables associated with male aging.

Adolescent↗

PubMed2001

Glycerol: a neglected variable in metabolic processes?

Glycerol is a small and simple molecule produced in the breakdown of glucose, proteins, pyruvate, triacylglycerols and other glycerolipid, as well as release from dietary fats. An increasing number of observations show that glycerol is probably involved in a surprising variety of physiopathologic mechanisms. Glycerol has long been known to play fundamental roles in several vital physiological processes, in prokaryotes and eukaryotes, and is an important intermediate of energy metabolism. Despite some differences in the details of their operation, many of these mechanisms have been preserved throughout evolution, demonstrating their fundamental importance. In particular, glycerol can control osmotic activity and crystal formation and then act as a cryoprotective agent. Furthermore, its properties make it useful in numerous industrial, therapeutic and diagnostic applications. Few studies have focussed directly on glycerol, however, and while its metabolism is increasingly well documented, much of the details remain unknown. Considering the importance of glycerol in multiple vital physiological processes, its study could help unlock important physiopathological mechanisms.

Amino Acid Sequence↗

PubMed2001

A sequence variation in the mitochondrial glycerol-3-phosphate dehydrogenase gene is associated with increased plasma glycerol and free fatty acid concentrations among French Canadians.

FAD-dependent glycerol-3-phosphate dehydrogenase (mGPD) enzyme is located in the mitochondrial inner membrane where it catalyzes irreversible oxidation reactions. Type 2 diabetes mellitus (DM) is a multifactorial disorder associated with physiological abnormalities in the glycerol and free fatty acids (FFA) metabolic pathways. In the present study, we have evaluated the association among the mGPD H264R sequence variation and postabsorptive plasma FFA and glycerol concentrations in a sample of French Canadians with and without type 2 DM. A sample of 81 recently diagnosed type 2 DM and 318 nondiabetic, nonobese, normotriglyceridemic French Canadians were screened for the presence of the mGPD H264R genetic variant using a PCR-RFLP-based method. The 318 nondiabetic subjects were free of known type 2 DM covariates (fasting glucose <7.0 mmol/L, body mass index <29 kg/m(2), fasting glycerol <2.0 mmol/L and absence of the N288D sequence variation in the glycerol kinase gene, fasting triglyceride <2.5 mmol/L). The association of mGPD H264R sequence variation with plasma FFA and glycerol concentrations was assessed in different regression models. Among non-DM individuals, the R allele (HR and RR genotypes) was associated with increased plasma FFA and glycerol concentrations (P < 0.05). However, the mean plasma FFA and glycerol concentrations were not affected by the H264R genotype in the type 2 DM sample. Overall, mean plasma FFA concentrations in non-DM RR homozygotes reached values that were similar to those achieved in patients with type 2 diabetes (0.87 +/- 0.63 vs 0.90 +/- 0.48 mmol/L). After controlling for age, gender, body mass index, fasting glucose, and fasting triglyceride concentrations, the relative odds of having fasting plasma FFA levels above the 90th percentile (0.9 mmol/L) in the absence of DM was increased by twofold in H264R heterozygotes (P = 0.04) and fourfold among R264 homozygotes (P = 0.009) compared to noncarriers. In the absence of DM, the mGPD R allele was also associated with higher plasma glycerol concentrations (P < 0.05). Results in non-DM individuals suggest that the mGPD R allele is associated with DM intermediate phenotypes. The absence of a relation between mGPD genotype and DM is in accordance with the view that DM is a complex phenotype in which increased plasma FFA or glycerol concentrations result from metabolic alterations which might obscure the effect of the mGPD polymorphism.

Adult↗

PubMed1988

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Canada↗