The impact of visceral fat on multiple risk factors and carotid atherosclerosis in chronic haemodialysis patients

Sir,

We read with much interest the original article by Yamauchi et al. [1] reporting the importance of visceral fat (VF) in carotid atherosclerosis, lipid abnormalities and hyperinsulinaemia in maintenance haemodialysis patients. In their study, the patients were separated into three groups according to VF content, and three groups were compared for well known atherosclerotic risk factors such as age, blood pressure, lipid levels, duration of haemodialysis, haemaodialysis efficiency (Kt/Vurea), fasting plasma glucose and insulin levels. They evaluated systemic atherosclerosis with carotid intima media thickness (CIMT), plaque score (PS) and stiffness parameter (SP) by high-resolution B-mode ultrasonography. All three methods shows that patients with higher VFA had greater carotid atherosclerotic changes. In this study, although VFA was not correlated with CIMT, it was correlated with PS and SP. Using multivariate regression analysis, they found that VFA was the strongest predictor of PS, but not SP and CIMT.

When looking at the relationship between VFA and lipid abnormalities and hyperinsulinaemia, it was clear that VF was a good predictor of metabolic disorder as it was shown in non-dialysis subjects. However, as stated in the Discussion (para 3), it seems to be difficult to conclude that VF had an additional risk for atherosclerotic disease and contributed to the accelerated atherosclerosis. As shown, VFA was highly correlated with well-known risk factors such as low high-density lipoprotein (HDL), high triglyceride and high plasma insulin levels. If there were a correlation analysis between these factors (HDL, plasma insulin, fasting glucose and triglyceride) and systemic atherosclerosis (CIMT, PS and SP), one would expect the existence of a correlation between metabolic factors and systemic atherosclerosis. In addition, the multivariate regression models including body mass index (BMI), SFA and VFA (independent variables) were performed to clarify which was the most strongly related to carotid atherosclerosis (PS, SP and CIMT taken as dependent variables). They found that only PS seems to be related to VFA and there was a very good correlation between blood lipids (HDL and triglyceride) and VFA.

In the same issue of the journal, London et al. showed that arterial intimal calcification (AIC) was much more correlated with classical atherosclerosis risk factors in comparison with patients with arterial media calcification (AMC). Whilst, CIMT, PS and SP were highest in the AIC group, age, duration of dialysis and lipids were the independent factors for AIC [2]. Therefore, as shown in this study of Yamauchi et al., in addition to these independent parameters (BMI, SFA and VFA), blood lipids and age should have been included in the multivariate model because of their possible effect on carotid atherosclerosis. Without including them in the analysis, it cannot be concluded reliably whether VFA have any independent significant impact on carotid atherosclerosis.

In a previous study, we showed the significant correlations between CIMT and age, left ventricular mass index, blood pressure and the ACE D allele. In multiple regression analysis, the risk factors for increased CIMT in haemodialysis patients were pre-dialysis systolic blood pressure and the ACE D allele in the additive model [3]. In the study of Yamauchi et al., whilst no significant difference in the three groups (according to VF) was noticed, there was a tendency that the high VF group was the oldest group. Since age is a well known risk factor for atherosclerosis, it would be interesting to see whether there was any correlation between systemic atherosclerosis measures (CIMT, SP and PS) and age in this study.

Conflict of interest statement. None declared.

Kenan Keven and Gokhan Nergizoglu

Ankara University School of Medicine Department of Nephrology Ankara Turkey Email: keven{at}medicine.ankara.edu.tr

References

  1. Yamauchi T, Kuno T, Takada H, Nagura Y, Kanmatsuse K, Takahashi S. The impact of visceral fat on multiple risk factors and carotid atherosclerosis in chronic haemodialysis patients. Nephrol Dial Transplant 2003; 18: 1842–1847[Abstract/Free Full Text]
  2. London GM, Guérin AP, Marchais SJ, Métivier F, Pannier B, Adda H. Arterial media calcification in end-stage renal disease: impact on all-cause and cardiovascular mortality. Nephrol Dial Transplant 2003; 18: 1731–1740[Abstract/Free Full Text]
  3. Nergizoglu G, Keven K, Gurses MA et al. Carotid intima-media thickness and ACE-gene polymorphism in hemodialysis patients. J Nephrol 1999; 12: 261–265[ISI][Medline]




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