The angiotensin-converting enzyme gene and the angiotensin II type I receptor gene as candidate genes for microalbuminuria. A study in nondiabetic and non-insulin-dependent diabetic subjects

Genetics of diabetic neuropathy: Systematic review, meta-analysis and trial sequential analysis

OBJECTIVE

Diabetic neuropathy (DN) is one of the most common complications of diabetes that occurs in more than 67% of individuals with diabetes. Genetic polymorphisms may play an important role in DN development. However, until now, the association between genetic polymorphisms and DN risk has remained unknown. We performed a systematic review, meta-analysis, and trial sequential analysis (TSA) of the association between all genetic polymorphisms and DN risk.

METHODS

Relevant published studies examining the relationship between all genetic polymorphisms and DN were obtained based on a designed search strategy up to 28 February 2019. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess overall pooled effects of genetic models as well as in subgroup analyses. Sensitive analysis and publication bias were applied to evaluate the reliability of the study. Moreover, TSA was conducted to estimate the robustness of the results.

RESULTS

We conducted a systematic review of a total of 1256 articles, and then 106 publications reporting on 136 polymorphisms of 76 genes were extracted. We performed 107 meta-analyses on 36 studies involving 12,221 subjects to derive pooled effect estimates for eight polymorphisms. We identified that ACE I>D, MTHFR 1298A/C, GPx-1 rs1050450, and CAT -262C/T were associated with DN, while MTHFR C677T, GSTM1, GSTT1, and IL-10 -1082G/A were not. Sensitivity analysis, funnel plot, and Egger's test displayed robust results. Furthermore, the results of TSA indicated sufficient sample size in studies of ACE, GPx-1, GSTM1, and IL-10 polymorphisms.

INTERPRETATION

Our study assessed the association between ACE I>D, MTHFR C677T, MTHFR 1298A/C, GPx-1 rs1050450, CAT -262C/T, GSTM1, GSTT1, and IL-10 -1082G/A polymorphisms and DN risk. We hope that the data in our research study are used to study DN genetics.

High prevalence of ACE DD genotype among north Indian end stage renal disease patients

BACKGROUND

The Renin-Angiotensin system (RAS) is a key regulator of both blood pressure and kidney functions and their interaction. In such a situation, genetic variability in the genes of different components of RAS is likely to contribute for its heterogeneous association in the renal disease patients. Angiotensin converting enzyme-1 (ACE-1) is an important component of RAS which determines the vasoactive peptide Angiotensin-II.

METHODS

In the present study, we have investigated 127 ESRD patients and 150 normal healthy controls from north India to deduce the association between ACE gene polymorphism and ESRD. The inclusion criteria for patients included a constantly elevated serum creatinine level above normal range (ranging from 3.4 to 15.8) and further the patients were recommended for renal transplantation. A total of 150 normal healthy controls were also genotyped for ACE I/D polymorphism. The criterion of defining control sample as normal was totally based on the absence of any kidney disease determined from the serum creatinin level. Genotyping of ACE I/D were assayed by polymerase chain reaction (PCR) based DNA amplification using specific flanking primers Based on the method described elsewhere.

RESULTS

The difference of DD and II genotypes was found highly significant among the two groups (p = 0.025; OR = 3.524; 95% CI = 1.54-8.07). The combined genotype DD v/s ID+II comparison validated that DD genotype is a high risk genotype for ESRD (p = 0.001; OR = 5.74; 95% CI limit = 3.4-8.5). However, no correlation was obtained for different biochemical parameters of lipid profile and renal function among DD and non DD genotype. Interestingly, approximately 87% of the DD ESRD patients were found hypertensive in comparison to the 65% patients of non DD genotype

CONCLUSION

Based on these observations we conclude that ACE DD genotype implicate a strong possible role in the hypertensive state and in renal damage among north Indians. The study will help in predetermining the timing, type and doses of anti-hypertensive therapy for ESRD patients.

A common variant in the ACE gene is associated with peripheral neuropathy in women with type 2 diabetes mellitus

AIMS

The D allele of the ACE I/D gene variant is associated with higher tissue and serum ACE activity. Previously, studies have suggested an association between the D allele with the microvascular complications of diabetes. The aim of this study was to explore the impact of this genotype in relation to clinically manifest peripheral neuropathy (PN) in a cohort of subjects with type 2 diabetes mellitus (type 2 DM).

METHODS

Five hundred and seventy-two Caucasian subjects (230 females, 342 males) with type 2 DM were recruited from the diabetes clinic at University College London Hospitals NHS Trust. Clinically manifest PN was determined from a standardized clinical examination.

RESULTS

The ACE I/D genotype distribution was in Hardy-Weinberg equilibrium. In the whole group, no significant association was seen between genotype and PN; however, when stratified by sex, the D allele was associated with PN in females but not in males. The odds ratio (OR) for PN in the D allele carriers compared to those homozygous for the I allele was significantly higher in females [OR 2.93 (1.09-7.63), P=.027] but not in males [OR 1.2 (0.61-2.36), P=.60].

CONCLUSIONS

The presence of the D allele is associated with increased risk of peripheral neuropathy in females but not in male subjects with type 2 DM, suggesting a role for the renin-angiotensin system in the development of PN.

Development of microalbuminuria in essential hypertension

During the past few years, microalbuminuria has become a prognostic marker for cardiovascular and/or renal risk in diabetic and nondiabetic subjects. In essential hypertensives, an increased transglomerular passage of albumin may result from several mechanisms--hyperfiltration, glomerular basal membrane abnormalities, endothelial dysfunction, and nephrosclerosis. Cross-sectional studies have demonstrated that the main factors related to microalbuminuria are blood pressure (BP) values and hyperinsulinemia, as an expression of insulin resistance. Genetics, obesity, and smoking, however, have also been implicated as determinants of microalbuminuria in some of the studies. Follow-up studies support the role of BP values and subtle alterations in glucose metabolism, although contributing roles need to be assessed in further studies. It seems that the significance of microalbuminuria in essential hypertension is much broader than expected, and several factors may influence the presence of microalbuminuria. Thus, to reverse microalbuminuria, and to reduce urine albumin excretion and cardiovascular and renal risk, a strategy of multiple approaches may be needed. Whether or not the multiple approaches need to be implemented from the beginning or step by step in an individual approach should be established in the near future.

Polymorphisms of the angiotensinogen gene and the outcome of microalbuminuria in essential hypertension: a 3-year follow-up study

BACKGROUND

The objective of this study was to analyse the relationship of polymorphisms of the angiotensinogen (AGT) gene with the changes in microalbuminuria during 3 years of antihypertensive treatment in a group of young adults with essential hypertension.

METHODS

Essential hypertensives, less than 50 years old, never previously treated with antihypertensive drugs and in the absence of diabetes mellitus were included. After the initial evaluation, patients were treated using only nonpharmacological measures (n=23), only beta-blockers (n=26), only angiotensin-converting enzyme inhibitors (ACEi) (n=57) or a combination of treatments (n=25). The office blood pressure, biochemical profile and urinary albumin excretion (UAE) were measured at the beginning and then yearly. The polymorphism A-6G of the AGT gene located in the promoter region was analysed.

RESULTS

In total, 131 patients, 35 (27%) microalbuminurics, were included. Although no significant differences in systolic blood pressure (SBP), diastolic blood pressure (DBP), fasting glucose and UAE were observed among genotypes at the initial examination, during the 3 years of antihypertensive treatment the slope values for the DBP, fasting glucose and UAE differed significantly despite no differences in the distribution of treatments being present. The subjects carrying the AA-6 genotype had the largest DBP decrease, but the lowest UAE reduction and the highest slope of glucose. Out of 35 initially microalbuminuric patients, 24 became normoalbuminuric and the lowest reduction rates were observed in subjects who carried the allele A-6. No interaction between the type of treatment and genotype was observed on the changes in UAE, BP or glucose values. In the subset of 57 patients treated with ACEi, the changes in UAE, BP and glucose had the same trend as was observed in the total population.

CONCLUSIONS

Subjects carrying the AA genotype of the A-6G AGT gene polymorphism are resistant to a reduction of microalbuminuria. Whether this can be attributed to a predisposition to glucose metabolic disturbance or not needs to be confirmed in further studies.

Insertion/deletion polymorphism of the ACE gene is associated with type 2 diabetes

In an attempt to examine the role of an ACE gene insertion/deletion (I/D) polymorphism in type 2 diabetes, we conducted a case-control association study among 132 couple-pairs from northern China. The genotype frequencies for II, ID, and DD were 39.8, 39.8, and 20.3%, respectively, in the case group and 44.8, 44.8, and 10.4% in the control group. The DD frequency was significantly higher in the case group than in the control group (chi(2)(1) = 4.77, P = 0.03), suggesting that the DD genotype is associated with an increased susceptibility to type 2 diabetes in our study population.

[Genes and coronary heart disease]

The causes of atherosclerotic cardiovascular disease have been intensely scrutinized for the last few decades. Since the classic risk factors have been found to be incomplete predictors of the disease, additional risk factors based on molecular genetics are now being sought. Polymorphisms are gene variations that have only modest effects on the function of coded proteins or enzymes. However, they are common and may be risk factors in the presence of environmental risk factors (cholesterol, stress, tobacco). Recent advances in molecular biology have made it possible to detect numerous polymorphisms that might have a detrimental effect on vascular biology, suggesting the hypothesis that multiple polymorphisms in the presence of environmental factors could act synergistically in the pathogenesis of atherosclerosis and coronary heart disease, which are typically polygenic and multifactorial diseases. In this review, the current status of our knowledge of polymorphisms and mutations potentially implicated in the mechanisms of coronary artery disease is discussed. Genotype/phenotype, gene-gene, and gene-environmental interactions related to lipid metabolism, the renin-angiotensin-aldosterone and adrenergic systems, insulin resistance, oxidative stress and endothelial function, inflammation and thrombosis are analyzed. Individual coronary risk might be related to the presence of a critical accumulation detrimental polymorphisms.

Angiotensin-converting enzyme gene polymorphism and microvascular complications in Turkish type 2 diabetic patients

The aim of this study was to investigate whether an association exists between the angiotensin converting enzyme (ACE) insertion/deletion (I/D) polymorphism and microvascular complications of type 2 diabetes mellitus in Turkish patients. A total of 239 type 2 diabetic patients and 138 sex and age matched control subjects were included into the study. The I/D polymorphism was determined by polymerase chain reaction (PCR). Nephropathy status was determined according to urinary albumin/creatinine ratio (microg/mg) (<30 normoalbuminuria, 30-300 microalbuminuria, >300 macroalbuminuria) and retinopathy was evaluated by fundoscopic examination and by flourescein fundus angiography. The distribution of ACE I/D polymorphism and allele frequencies in diabetic patients were not significantly different from controls, DD genotype 32.2 versus 37.2%; ID genotype 50.6 versus 47.1%; and II 17.2 versus 15.2%; D allele 57.5 versus 61.2%; I allele 42.5 versus 38.8%. Genotype distribution between normo-, micro- and macroalbuminuric patients did not differ significantly (DD:ID:II (%), normoalbuminuria, 35:46:19; microalbuminuria, 28:55:17; macroalbuminuria, 31:55:14). There was also no difference in genotype distribution between patients with and without retinopathy (DD:ID:II (%), retinopathy positive, 32:51:17; retinopathy negative, 33:49:18). In conclusion, the ACE I/D polymorphism does not seem to be associated with diabetic nephropathy and retinopathy in Turkish type 2 diabetic patients.

Genetic polymorphisms in the renin-angiotensin system: relevance for susceptibility to cardiovascular disease

The renin-angiotensin system plays an important role in the pathogenesis of cardiovascular disease. Cloning of the human genes coding for the angiotensin-converting enzyme, angiotensinogen, and angiotensin II type 1 receptor has led to the discovery of several polymorphisms, which may be implicated in the pathogenesis of cardiovascular disease. The deletion/insertion (D/I) polymorphism of the angiotensin-converting enzyme gene is associated with hypertension in men, left ventricular hypertrophy in untreated hypertensive patients, various atherosclerotic cardiovascular complications, and microvascular disorders. The M235T polymorphism of the angiotensinogen gene may be associated with a higher risk of hypertension. The A1166C polymorphism of the angiotensin II type 1 receptor gene is probably correlated with hypertension and through an epistatic interaction with the D/I polymorphism of the angiotensin-converting enzyme gene possibly also with coronary heart disease. Several other gene polymorphisms, in particular those in the promoter area of the angiotensinogen gene, have been studied in relation to cardiovascular disease. Based on the insights gained from the reports summarized in this review article, population-based genetic studies of nuclear families are currently being conducted in Belgium and in the People's Republic of China with blood pressure and hypertension as the main outcome variables.

The effect of novel polymorphisms in the interleukin-6 (IL-6) gene on IL-6 transcription and plasma IL-6 levels, and an association with systemic-onset juvenile chronic arthritis

During active disease, patients with systemic-onset juvenile chronic arthritis (S-JCA) demonstrate a rise and fall in serum interleukin-6 (IL-6) that parallels the classic quotidian fever. To investigate the possibility that this cytokine profile results from a difference in the control of IL-6 expression, we examined the 5' flanking region of the IL-6 gene for polymorphisms. A G/C polymorphism was detected at position -174. In a group of 383 healthy men and women from a general practice in North London, the frequency of the C allele was 0.403 (95% confidence interval 0.37-0.44). In comparison, 92 patients with S-JCA had a different overall genotype frequency, especially those with onset of disease at < 5 yr of age. This was mainly due to the statistically significant lower frequency of the CC genotype in this subgroup. When comparing constructs of the 5' flanking region (-550-+61 bp) in a luciferase reporter vector transiently transfected into HeLa cells, the -174C construct showed 0.624+/-0.15-fold lower expression than the -174G construct. After stimulation with LPS or IL-1, expression from the -174C construct did not significantly change after 24 h, whereas expression from the -174G construct increased by 2.35+/-0.10- and 3.60+/-0.26-fold, respectively, compared with the unstimulated level. Plasma levels of IL-6 were also measured in 102 of the healthy subjects, and the C allele was found to be associated with significantly lower levels of plasma IL-6. These results suggest that there is a genetically determined difference in the degree of the IL-6 response to stressful stimuli between individuals. The reduced frequency of the potentially protective CC genotype in young S-JCA patients may contribute to its pathogenesis. Similarly the individual's IL-6 genotype may be highly relevant in other conditions where IL-6 has been implicated, such as atherosclerosis.