Altered phosphate metabolism in HIV-1-infected patients: another feature of metabolic syndrome?

Purpose of the study Metabolic syndrome represent a cluster of cardiovascu- lar risk factors that has become a serious problem for HIV-1-infected patients. It was proposed that distur- bances in phosphate metabolism may represent a key feature of metabolic syndrome. Because phosphate is involved directly in carbohydrate metabolism, hypopho- sphatemia can results in impaired utilization of glucose, insulin resistance and hyperinsulinemia. Thus, we undertook the present study to investigate the relation- ship between phosphate levels and the presence of the characteristics of metabolic syndrome, as well as the mechanism that may be responsible for reduced phos- phate levels in patients with this syndrome. Methods 130 HIV-1-infected patients were consecutively enrolled in a prospective, cross-sectional, single centre study. All patients were receiving HAART for more than six months. We selected two groups: HIV+ patients with metabolic syndrome (group A, n=86) and HIV+ patients without metabolic syndrome (group B, n=44). The diag- nosis of metabolic syndrome was based on Adult Treat- ment Panel III guidelines. Demographic characteristics, metabolic variables, duration of Tenofovir therapy, dura- tion of HAART, CD4 and viral load were collected. Kid- ney tubular function was examined using tubular resorption of phosphate and normalized renal threshold phosphate concentration. Summary of results Patients with metabolic syndrome showed significantly lower phosphate (3.13 mg/dl vs 3.55 mg/dl, p<0.01) and higher insulin (13.2 mg/dl vs 6.9 mg/dl, p<0.01) levels compared with controls. There was a linear significant decrease in phosphate values as the number of compo- nents of metabolic syndrome increased (p<0.001). Multi- ple regression analysis including all 5 components of metabolic syndrome and months of TDF treatment showed that insulin level was the most discriminant of serum phosphate (r= -0.22, p<0.01). Figure 1 Conclusions Our preliminary data demonstrated that HIV-1-infected patients with metabolic syndrome showed significantly lower phosphate levels compared with HIV-1-infected patients without metabolic syndrome regardless of teno- fovir based therapy. The clinical significance of these disturbances, as well as their importance as target for preventive or therapeutic interventions, remains to be established.