The effect of age and a high-fat, high-carbohydrate diet on the development of arterial hypertension and kidney disease in the experiment

Aim. To identify the structural foundations of the pathogenesis of arterial hypertension and kidney disease associated with a high-fat, high-carbohydrate diet and age.

Materials and methods. The study was carried out on male Wistar rats aged 60 and 450 days. The animals were divided into 4 groups: group 1 (n = 14) – intact rats (60 days old) fed with a standard diet for 90 days; group 2 (n = 14) – rats (aged 60 days) receiving a high-fat, high-carbohydrate diet for 90 days; group 3 (n = 14) – intact rats (aged 450 days) receiving a standard diet for 90 days; group 4 (n = 14) – rats (aged 450 days) fed with a high-fat, high-carbohydrate diet for 90 days. Clinical and instrumental research methods, enzyme-linked immunosorbent assay, and immunohistochemistry and histology techniques were used in the study.

Results. Feeding 60-day-old animals with a high-fat, high-carbohydrate diet resulted in an increase in body weight and abdominal fat, a rise in systolic blood pressure, and moderately pronounced histologic changes in the kidneys. In intact 450-day-old rats, age-related changes prevailed: changes in the myocardial mass, an increase in TGF-β1, morphological changes in the renal tubules and glomeruli. In 450-day-old rats receiving a high-fat, highcarbohydrate diet, the most pronounced increase in both systolic and diastolic blood pressure, a significant rise in serum fibronectin, and destructive changes in the renal tissue were noted.

Conclusion. Functional and biochemical signs of arterial hypertension and morphological changes in the kidneys were the most pronounced in 450-day-old rats fed with a high-fat, high-carbohydrate diet.

Dual renin-angiotensin system blockade for nephroprotection

In experimental diabetic and nondiabetic chronic kidney disease, angiotensin-converting enzyme (ACE) inhibitor and angiotensin receptor blockers (ARB) combination therapy reduce proteinuria and prevent structural lesions more effectively than either drug alone. Consistently, in humans, a multidrug individually tailored antiproteinuric treatment based on combination therapy with maximum tolerated doses of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers ("Remission Clinic") reduced proteinuria and prevented end-stage renal disease more effectively than angiotensin-converting enzyme/angiotensin receptor blockers monotherapy, in particular in subjects with nondiabetic chronic kidney disease. Fixed doses of an angiotensin-converting enzyme inhibitor or renin inhibitor added-on losartan failed to exert any additional renoprotective effect as compared with losartan monotherapy in patients with type 2 diabetes and overt nephropathy. However, the VA NEPHRON D study found that losartan and lisinopril combination therapy reduced by 34 % the risk of pre-defined reductions in estimated glomerular filtration rate, end-stage renal disease or death as compared to losartan in 1448 type 2 diabetes patients with overt nephropathy. Unfortunately, treatment effect failed to achieve the nominal significance (P=0.07) because of premature trial interruption. Thus, the Remission Clinic protocol is the most powerful tool to prevent progression to end-stage renal disease in nondiabetic proteinuric chronic kidney disease. Results of the ongoing VALID trial will show whether this approach can be safely extended to type 2 diabetes patients.

Angiotensin II type 1 receptor antagonists in animal models of vascular, cardiac, metabolic and renal disease

We have reviewed the effects of angiotensin II type 1 receptor antagonists (ARBs) in various animal models of hypertension, atherosclerosis, cardiac function, hypertrophy and fibrosis, glucose and lipid metabolism, and renal function and morphology. Those of azilsartan and telmisartan have been included comprehensively whereas those of other ARBs have been included systematically but without intention of completeness. ARBs as a class lower blood pressure in established hypertension and prevent hypertension development in all applicable animal models except those with a markedly suppressed renin-angiotensin system; blood pressure lowering even persists for a considerable time after discontinuation of treatment. This translates into a reduced mortality, particularly in models exhibiting marked hypertension. The retrieved data on vascular, cardiac and renal function and morphology as well as on glucose and lipid metabolism are discussed to address three main questions: 1. Can ARB effects on blood vessels, heart, kidney and metabolic function be explained by blood pressure lowering alone or are they additionally directly related to blockade of the renin-angiotensin system? 2. Are they shared by other inhibitors of the renin-angiotensin system, e.g. angiotensin converting enzyme inhibitors? 3. Are some effects specific for one or more compounds within the ARB class? Taken together these data profile ARBs as a drug class with unique properties that have beneficial effects far beyond those on blood pressure reduction and, in some cases distinct from those of angiotensin converting enzyme inhibitors. The clinical relevance of angiotensin receptor-independent effects of some ARBs remains to be determined.

Combination of Telmisartan and Linagliptin Preserves Pancreatic Islet Cell Function and Morphology in db/db Mice

OBJECTIVES

The present study aimed to investigate the synergistic action of telmisartan and linagliptin in ameliorating pancreatic islet functions and morphology in type 2 diabetes mellitus and to delineate the molecular signaling pathway involved.

METHODS

db/db mice were given telmisartan (3 mg/kg) or linagliptin (3 mg/kg) alone or in combination, daily for 8 weeks, and were studied in vivo by fasting and random blood glucose tests, oral glucose tolerance tests, and intraperitoneal insulin tolerance tests, as well as ex vivo by glucose-stimulated insulin secretion and morphology of pancreatic islets. The underlying signaling pathways were examined by Western blot, real-time quantitative polymerase chain reaction, and dihydroethidium staining analyses using mouse pancreatic islets and rat β-insulinoma cells.

RESULTS

Telmisartan/linagliptin combination induced significantly better glucose homeostasis than the monotherapies. Posttreatment reactive oxygen species level was suppressed most significantly after the telmisartan/linagliptin combined therapy, whereas no significant change in peroxisome proliferator-activated receptor γ expressions was observed after treatments.

CONCLUSIONS

The telmisartan/linagliptin combination preserved pancreatic islet cell functions and morphology via reduction of oxidative stress but independent of the peroxisome proliferator-activated receptor γ pathway. Our data shed light on the therapeutic potential of using the telmisartan/linagliptin combination in the treatment of human type 2 diabetes mellitus and its related complications.

The Blocking on the Cathepsin B and Fibronectin Accumulation in Kidney Glomeruli of Diabetic Rats

Hyperglycemia results in the activation of tissue angiotensin II. Angiotensin II stimulates the synthesis of ECM proteins and causes a decrease activity of proteolytic enzymes. The aim of this study was to assess the impact of multilevel blocking of the RAAS, cathepsin B activity, and fibronectin accumulation in the glomerular in the rats diabetes model. Sixty male Wistar rats were initially included. Diabetes was induced by intravenous administration of streptozotocin. The animals were randomized to six groups of ten rats in group. Rats in the four groups were treated with inhibitors of the RAAS: enalapril (EN), losartan (LOS), enalapril plus losartan (EN + LOS), and spironolactone (SPIR); another group received dihydralazine (DIH) and the diabetic rats (DM) did not receive any drug. After six weeks, we evaluated blood pressure, 24 h urine collection, and blood for biochemical parameters and kidneys. In this study, fluorometric, ELISA, and immunohistochemical methods were used. Administration of EN + LOS increased activity of cathepsin B in homogenates of glomeruli compared to DM. Losartan treatment resulted in reduction of the ratio kidney weight/body weight compared to untreated diabetic rats. SPIR resulted in the increase activity of cathepsin B in the homogenate of glomeruli. The values of cathepsin B in the plasma of rats in all studied groups were similar and showed no tendency.

Dual renin-angiotensin system blockade for nephroprotection: still under scrutiny

In experimental diabetic and non-diabetic chronic kidney disease (CKD), angiotensin-converting enzyme inhibitor (ACEi) and angiotensin receptor blocker (ARB) combination therapy reduces proteinuria and prevents structural lesions more effectively than either drug alone. Consistently, in humans, a multidrug individually tailored antiproteinuric treatment based on combination therapy with maximum tolerated doses of ACEi and ARB (Remission Clinic protocol) reduced proteinuria and prevented end-stage renal disease (ESRD) more effectively than ACEi/ARB monotherapy, in particular in subjects with non-diabetic CKD. Fixed doses of an ACEi or renin inhibitor added to losartan failed to exert any additional renoprotective effect as compared with losartan monotherapy in patients at increased cardiovascular risk (ONTARGET study) or with type 2 diabetes and overt nephropathy (ALTITUDE study). The VA NEPHRON D study found that losartan and lisinopril combination therapy reduced by 34% the risk of predefined reductions in estimated glomerular filtration rate, ESRD or death as compared to losartan in 1,448 type 2 diabetes patients with overt nephropathy. Unfortunately, the treatment effect failed to achieve the nominal significance (p = 0.07) because of premature trial interruption. Thus, the Remission Clinic protocol is the most powerful tool to prevent progression to ESRD in non-diabetic proteinuric CKD. Results of the ongoing VALID trial will show whether this approach can be safely extended to type 2 diabetes patients.