Plasma homocysteine levels in indigenous Australians

Homocysteine in Renal Transplant Recipients: Association with Transplant Duration and Renal Function

BACKGROUND

Hyperhomocystinemia is an established risk factor for cardiovascular events and has been identified as an important cause of morbidity and mortality in renal transplant recipients. This investigation was aimed to determine the effect of age and transplant duration on serum total homocysteine (tHcy) levels in renal transplant recipients.

METHODS

We analyzed serum levels of tHcy, albumin, alkaline phosphatase, alanine transferase, bilirubin, calcium, corrected calcium, cholesterol, creatinine, folate, phosphate, potassium, sodium, triglycerides, urea and vitamin B12 in 88 transplant patients (ages, 14-67 years; transplant duration, 1-252 months) and 60 control subjects.

RESULTS

Our results showed significant hyperhomocystinemia in transplant patients (19.92 +/- 0.72) as compared to controls (9.28 +/- 0.25), while male subjects in both groups had significantly higher tHcy than females. There was no correlation between patients' age and serum tHcy, whereas the time after transplantation was significantly correlated with tHcy (r=0.318, P<0.01). A significant correlation was observed between tHcy and serum urea, creatinine, vitamin B12 and potassium in renal transplant patients.

CONCLUSION

This study clearly demonstrated significant hyperhomocystinemia and renal impairment in transplant recipients. A time-course increase in serum tHcy during posttransplant duration warrants long-term monitoring of patients for effective clinical management.

Homocysteine, renal disease and cardiovascular disease in a remote Australian Aboriginal community

BACKGROUND

Rates of renal and cardiovascular disease are high among Aboriginal Australians living in remote communities. Nutritional problems, in particular low folate levels, are also common. This suggests that increased homocysteine concentrations might be widespread, and a possible contributor to the high rates of cardiovascular disease.

AIMS

To examine homocysteine concentrations, and their relationships to folate levels, and to markers of renal disease and cardiovascular disease in a remote Aboriginal Australian community

METHODS

As part of a cross-sectional survey among adults in one community, homocysteine concentrations, concentrations of the crucial determinants (red blood cell (RBC) folate, vitamin B(12) and the C677T methylene tetrahydrofolate reductase polymorphism) and cardiovascular risk factors were examined.

RESULTS

Among 221 people, geometric mean homocysteine concentration was 11.8 micromol/L (range: 11.1-12.5 micromol/L), with 57/221 (26%) values > or =15.0 micromol/L. Higher concentrations were associated with older age, male gender, lower RBC folate and lower vitamin B(12) concentrations and homozygosity for C677T. Homocysteine concentrations were not related to the presence of albuminuria, other than over the overt albuminuria range. Homocysteine concentrations were inversely correlated with calculated glomerular filtration rate (GFR). Carotid intima-media thickness, however, was not related to homocysteine concentration. In multivariate analyses, age, male gender, lower RBC folate concentrations, lower vitamin B(12) concentrations, lower calculated GFR and the C677T polymorphism were all associated with homocysteine concentrations.

CONCLUSIONS

Homocysteine concentrations were consistent with previous limited reports in Aboriginal communities. Although superficially they are similar to reports from non-Aboriginal settings, the younger age of this cohort and the association of homocysteine concentrations with age suggest that age-specific concentrations are higher among Aboriginal Australians. In addition to dietary determinants, the high prevalence of apparently reduced renal function renal disease appears to be an important determinant of homocysteine concentrations in remote Aboriginal communities. The role of homocysteine concentrations as a potential mediator of the high rates of cardiovascular disease remains to be determined.

The haematology of indigenous Australians

Prior to European settlement indigenous Australians were hunter-gatherers who lived in geographically isolated small clan groups, also separated by elaborate totemic rules. Today they still reside in isolated communities throughout Australia but many have moved to the cities. They share a high incidence of a range of health problems including cardiovascular disease, renal disease and infectious diseases largely attributed to a change to a more sedentary lifestyle. This paper reviews the haematology of indigenous Australians, including blood count, frequency and causes of anaemia, inherited risk factors for thrombophilia, blood groups and the incidence and types of haematological malignancies. There are some significant genetic differences between indigenous and non-indigenous Australians particularly in the frequency of blood groups, factor V Leiden and prothrombin mutations and presence of -alpha3.7 kb thalassaemia. These findings may have practical therapeutic implications (e.g. HPA phenotype for transfusion therapy and pregnancy risk) and in predicting disease risk. Other differences are acquired, related to lifestyle and living conditions (e.g. eosinophilia secondary to parasitic infections; iron and folate deficiencies), and are largely preventable.

Biochemical Indicators of Nutritional Status and Dietary Intake in Costa Rican Cabécar Indian Adolescents

The purpose of this study was to determine the blood levels of selected nutritional status indicators and the dietary intake of Costa Rican Cabécar Indians aged 10 to 16 years. The results showed that 65% of the adolescents had an adequate body mass index (BMI) for their age, and 32% had a BMI < 5th percentile. Likewise, the study revealed a high prevalence of anemia (57%), deficient serum folate levels (54%), deficient vitamin B12 levels (31%), and subclinical vitamin A deficiency (10%). Additionally, the youngsters had elevated prevalences of high triglyceride levels (77%), borderline high-density lipoprotein (HDL) cholesterol levels (46%), homocysteine levels > 10 μmol/L (29%), and homozygous mutation of methylenetetrahydrofolate reductase (MTHFR) (49%). The diet was poor, being high in saturated fat and low in polyunsaturated fat, fiber, and several micronutrients. The dietary intakes of more than 55% of the adolescents did not meet 50% of the estimated average requirements (EAR) for zinc, vitamin A, vitamin C, vitamin B12, vitamin B2, and folate. Furthermore, a high prevalence of parasitosis was found (68%). Our results show an adolescent Cabécar population with a mosaic of nutritional deficiencies and cardiovascular risk factors.

Interfaces between cardiovascular and kidney disease among Aboriginal Australians

Rates of kidney disease among several indigenous groups have been shown to be substantially higher than corresponding non-indigenous groups. This excess has been clearly shown among Aboriginal Australians with respect to both end-stage kidney disease and early kidney disease. Rates of cardiovascular disease among Aboriginal Australians are also very high, as are rates of diabetes, smoking, and possibly overweight and obesity. These factors have been traditionally linked with cardiovascular and renal disease as part of a broader "metabolic syndrome." However, the links and interfaces between cardiovascular and kidney disease in this environment extend beyond these "traditional" factors. The factors associated with atherosclerosis have expanded in recent years to include markers of inflammation, some infection, antioxidants, and other "non-traditional" risk factors. Given the high rates of acute infection and poor living conditions endured by many indigenous people, one might expect these "non-traditional" risk factors to be highly prevalent. In this review, we explore the relationships between markers of inflammation, some serological markers of infection, and other selected markers and both cardiovascular and renal disease. In doing so, we demonstrate links between kidney and cardiovascular disease at a number of levels, beyond the "traditional" cardiovascular/renal risk factors. Many of these factors are beyond the control of the individual or even community; addressing these issues a broader focus and biopsychosocial model.

Correlation between C677T MTHFR gene polymorphism, plasma homocysteine levels and the incidence of CAD

The lesions of coronary atherosclerosis represent the result of a complex, multicellular, inflammatory-healing response in the coronary arterial wall. In vivo and in vitro cellular and molecular studies have suggested a role for tissue homocysteine in endothelial cell injury and adverse extra-cellular matrix remodeling. Gene polymorphisms in relation with numerous risk factors might increase the incidence of coronary artery disease (CAD). In this review we have focused on the correlations between plasma homocysteine levels, the incidence of cardiovascular disease and the cytosine-to-thymidine substitution at nucleotide 677 (C677T) of the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene, coding for a key enzyme in methionine-homocysteine metabolism. The role of the C677T MTHFR gene polymorphism in the causation of CAD is controversial. We reviewed 12 recent case-control studies comprising 5370 genotyped patients with CAD and 4961 genotyped participants without CAD. There was no significant difference between those with and without CAD in the frequency of the C677T polymorphism (34.9 vs 33.6%). The frequency of homozygous C677T polymorphism in these groups was 10.9 versus 12.8%, respectively, although there were some ethnic differences in the C677T MTHFR polymorphism. In the analysis of the 12 studies, the odds ratio of CAD associated with the TT genotype (homozygous C677T polymorphism) was 1.18. Only slightly higher plasma homocysteine levels were observed in participants with the val/val (TT) genotype (14.4+/-2.9 micro mol/L in TT genotype vs 11.1+/-1.9 and 11.9+/-2 micro mol/L in CC and CT genotype, respectively). In addition, the relation between homocysteine increase after methionine loading and MTHFR genotypes is also controversial. However, hyperhomocysteinemia because of the C677T MTHFR allele may be corrected with oral folic acid therapy. Further investigations on the relationships between MTHFR genotypes and the incidence of CAD should be based on larger samples, paying attention to the differences between various ethnic populations. Individual therapeutic strategies based on single nucleotide polymorphism may become increasingly important for preventive treatment against polygenic CAD.

Homocysteine: An aetiological contributor to peripheral vascular arterial disease

Surgeons are increasingly being exposed to the term 'hyperhomocysteinaemia' but few understand this condition that affects up to 10% of the population, or its pathological sequelae. Hyperhomocysteinaemia has been identified as an important and independent risk factor for atherosclerosis. There is increasing evidence that, in addition to coronary disease, hyperhomocysteinaemia is also associated with an increased risk of developing peripheral arterial disease. Causes of elevated homocysteine levels include inherited enzyme deficiencies and acquired vitamin deficiencies. Detection of hyperhomocysteinaemia is particularly relevant in patients with early onset atherosclerosis. Effective lowering of elevated homocysteine levels is possible with folate, vitamin B6 and B12 supplementation and may reduce the incidence and sequelae of atherosclerotic peripheral arterial disease.

Effect of smoking on serum concentrations of total homocysteine and B vitamins in mid-pregnancy

There are conflicting findings in the literature on the effect of smoking on total homocysteine (tHcy) concentrations in non-pregnant subjects. We evaluated the effect of smoking on serum concentrations of tHcy, folate, vitamin B-12 pyridoxal 5'-phosphate (PLP, a coenzyme form of vitamin B-6) in 196 women at 18 and 30 weeks' gestation. The smokers were defined as those who self-reported cigarette smoking and had serum concentrations of thiocyanate, a biomaker of smoking, in the highest quartiles of the population. Mid-pregnancy serum tHcy concentrations were not significantly different between smokers and non-smokers. Folate, vitamin B-12 and PLP concentrations were generally lower in smokers than non-smokers. In smokers, tHcy concentrations had significant negative correlations with folate at both time points. The multiple regression analyses indicated that serum folate concentration was the most significant factor associated with tHcy concentrations among smokers, whereas thiocyanate concentrations showed no such effect. We conclude that serum tHcy concentrations were most strongly associated with the nutritional status of folate among the B vitamins tested during mid-pregnancy in our subjects. We suggest that it is essential to consider the nutritional status of folate, vitamin B-12 and vitamin B-6 in evaluating the effect of smoking on homocysteine metabolism.