ARB medications, including telmisartan, are widely used for people with CKD undergoing HD, to reduce the impact of cardiovascular complications. It thought that activation of the renin-angiotensin-aldosterone system (RAAS) causes endothelial dysfunction to trigger the development of cardiovascular complications in this context, particularly congestive heart failure (CHF) and left ventricular hypertrophy (LVH). This is indicated by increased levels of angiotensin II and aldosterone as the major mediator of the RAAS. Therefore, ACEI and ARB have become the first line agents to treat hypertension in CKD patients undergoing hemodialysis [9]. Telmisartan also appears to provide other benefits in lowering insulin resistance [10].
In the present study, insulin resistance was observed for more patients with a medical history of diabetes mellitus than non-diabetic patients before the administration of telmisartan, similar to the findings of Takenaka et al. in 2007 [1]. Other research has also revealed an elevated incidence of increased insulin resistance in CKD patients with hemodialysis, finding a linear correlation between decreased creatinine clearance (CrCl) and significantly increased insulin resistance in patients having CrCl below 60 ml/min. [2].
The results from our study showed that the mean HOMA-IR value declined significantly by (34.32%) from 1.69 to 1.11 after 3 months (p < 0.05), suggesting that telmisartan has potential activity in reducing insulin resistance amongst people with dialysis-dependent CKD. The results are consistent with previous findings amongst people with less severe CKD not requiring dialysis [6, 7, 8]. Decreased insulin resistance observed in this study suggests a positive effect of telmisartan in improving insulin sensitivity in CKD-HD patients as showed by decreased plasma insulin, suggesting a lower need of insulin to maintain fasting plasma glucose. This effect of telmisartan may be based on its effect as a partial agonist of peroxisome proliferator-activated receptor Ɣ (PPARƔ), one of the nuclear hormone receptors that plays a major role as a transcription factor regulating the metabolism of carbohydrates, fats, and inflammation. PPAR Ɣ presents commonly in adipose tissues and small amounts in various cells of vascular smooth muscle, endothelium, and monocytes [10]. This activity may be associated with the chemical structure of telmisartan, which resembles the structure of pioglitazone (a thiazolidinedione compound), and thus telmisartan has been found to have approximately 25–30% of the activity of pioglitazone in activating PPARƔ [10]. PPARƔ activation can increase the expression of a wide variety of genes and enzymes involved in the metabolism of carbohydrates (adiponectin, glucokinase and glucose transporter–4) and the metabolism of fat (lipoprotein lipase, adipocyte fatty acid transporter protein, fatty-acyl-CoA synthase, and malic enzyme). In addition, activation of PPARƔ can also suppress the activity of pro-inflammatory cytokine tumor necrosis factor-α which can suppress the sensitivity of insulin through insulin signal transduction disorder [10].
This study has a range of limitations. The sample size was small, limiting the extent to which it is possible generalize to larger populations. Patient self-report about telmisartan adherence was used and might have overestimated the extent of adherence. Further research is needed with a larger sample size, multicenter setting, and longer duration of follow-up. Future studies could be designed to address specific inclusion criteria to assess specific issues that might cause changes in insulin resistance. In the meantime, this preliminary data suggests that telmisartan appears to be a reasonable choice of antihypertensive agent for dialysis dependent patients.