Adiponectin gene polymorphisms and susceptibility to diabetic nephropathy: a meta-analysis

ADIPOQ rs2241766 Gene Polymorphism and Predisposition to Diabetic Kidney Disease

BACKGROUND

This meta-analysis was performed to obtain a more comprehensive estimation of the role of the single nucleotide polymorphism (SNP) rs2241766 in the ADIPOQ gene in the occurrence of diabetic kidney disease (DKD).

METHODS

Relevant studies were identified from digital databases such as Embase, PubMed, Medline, Cochrane Library, Google Scholar, WanFang, and Chinese National Knowledge Infrastructure (CNKI). Odds ratios (ORs) with their corresponding 95% confidence intervals (95% CIs) were pooled by means of fixed- or random-effects models. Interstudy heterogeneity was examined using the Q test and I ² statistic, and sensitivity analysis was implemented to test the statistical stability of the overall estimates. Begg's funnel plot and Egger's test were applied to inspect potential publication bias among the included studies.

RESULTS

The overall ORs reflected a positive correlation between the ADIPOQ rs2241766 polymorphism and susceptibility to DKD in the GG vs. TT and GG vs. TT+TG comparisons (OR = 1.51, 95%CI = 1.16 - 1.95; OR = 1.43, 95%CI = 1.11 - 1.85). After stratification analyses by ethnicity and disease type, a similar trend was also revealed in the Caucasian and African subgroups as well as in the type 2 diabetes mellitus (T2DM) subgroup.

CONCLUSION

The ADIPOQ rs2241766 polymorphism may be associated with an increased risk of DKD, especially in Caucasian and African populations as well as in T2DM patients.

Evolving spectrum of diabetic nephropathy

Diabetes remains an important health issue as more patients with chronic and uncontrolled diabetes develop diabetic nephropathy (DN), which classically presents with proteinuria followed by a progressive decrease in renal function. However, an increasing proportion of DN patients have a decline in kidney function and vascular complications without proteinuria, known as non-proteinuric DN (NP-DN). Despite the increased incidence of NP-DN, few clinical or experimental studies have thoroughly investigated the pathophysiological mechanisms and targeted treatment for this form of DN. In this review, we will examine the differences between conventional DN and NP-DN and consider potential pathophysiological mechanisms, diagnostic markers, and treatment for both DN and NP-DN. The investigation of the pathophysiology of NP-DN should provide additional insight into the cardiovascular factors influencing renal function and disease and provide novel treatments for the vascular complications seen in diabetic patients.

Genetic variants in promoter regions associated with type 2 diabetes mellitus: A large-scale meta-analysis and subgroup analysis

BACKGROUND

Promoter plays important roles in regulating transcription of genes. Association studies of genetic variants in promoter region with type 2 diabetes (T2D) risk have been reported, but most were limited to small number of individual genetic variants and insufficient sample sizes. In addition, the effect of study populations and demographic characteristics were often neglected.

METHODS

In this study, we conducted a large-scale meta-analysis and subgroup analysis of T2D associated genetic variants in the promoter regions to evaluate their contribution to the susceptibility in T2D. Alleles and genotypes from cohort or case-controlled studies were extracted for future study. Total 41 742 cases and 50 493 controls for three loci were involved in 70 articles.

RESULTS

Seventy case-controlled studies of three genes with 41 742 cases and 50 493 controls were included. Meta-analysis showed only rs266729 and rs17300539 of ADIPOQ, and rs1884613, rs2144908, and rs4810424 of HNF4A were significantly associated with T2D risk. Subgroup analysis showed that both rs266729 and rs17300539 of ADIPOQ were associated with the risk of T2D in Caucasian population, but only rs266729 of ADIPOQ in Asian population and rs2144908 in other population including multinational North American. For diagnostic criteria, rs266729 of ADIPOQ and rs2144908 of HNF4A were associated with T2D risk when WHO/ADA diagnostic criteria were used. For genotyping methods, both rs266729 of ADIPOQ and rs2144908 of HNF4A were associated with T2D risk when other than Taqman and Sequencing methods were used.

CONCLUSIONS

T2D was significantly associated with promoter rs266729, rs17300539, rs1884613, rs2144908, and rs4810424, and the association of T2D risk were affected by study population, diagnostic criteria, and genotype methods.

Novel Genetic Actors of Diabetes-Associated Microvascular Complications: Retinopathy, Kidney Disease and Neuropathy

Both type 1 and type 2 diabetes mellitus can lead to the common microvascular complications of diabetic retinopathy, kidney disease, and neuropathy. Diabetic patients do not universally develop these complications. Long duration of diabetes and poor glycemic control explain a lot of the variability in the development of microvascular complications, but not all. Genetic factors account for some of the remaining variability because of the heritability and familial clustering of these complications. There have been a large number of investigations, including linkage studies, candidate gene studies, and genome-wide association studies, all of which have sought to identify the specific variants that increase susceptibility. For retinopathy, several genome-wide association studies have been performed in small or midsize samples, but no reproducible loci across the studies have been identified. For diabetic kidney disease, genome-wide association studies in larger samples have been performed, and loci for this complication are beginning to emerge. However, validation of the existing discoveries, and further novel discoveries in larger samples is ongoing. The amount of genetic research into diabetic neuropathy has been very limited, and much is dedicated to the understanding of genetic risk factors only. Collaborations that pool samples and aim to detect phenotype classifications more precisely are promising avenues for a better explanation of the genetics of diabetic microvascular complications.

Diabetic nephropathy - complications and treatment

Diabetic nephropathy is a significant cause of chronic kidney disease and end-stage renal failure globally. Much research has been conducted in both basic science and clinical therapeutics, which has enhanced understanding of the pathophysiology of diabetic nephropathy and expanded the potential therapies available. This review will examine the current concepts of diabetic nephropathy management in the context of some of the basic science and pathophysiology aspects relevant to the approaches taken in novel, investigative treatment strategies.

Comprehensive approach to diabetic nephropathy

Diabetic nephropathy (DN) is a leading cause of mortality and morbidity in patients with diabetes. This complication reflects a complex pathophysiology, whereby various genetic and environmental factors determine susceptibility and progression to end-stage renal disease. DN should be considered in patients with type 1 diabetes for at least 10 years who have microalbuminuria and diabetic retinopathy, as well as in patients with type 1 or type 2 diabetes with macroalbuminuria in whom other causes for proteinuria are absent. DN may also present as a falling estimated glomerular filtration rate with albuminuria as a minor presenting feature, especially in patients taking renin-angiotensin-aldosterone system inhibitors (RAASi). The pathological characteristic features of disease are three major lesions: diffuse mesangial expansion, diffuse thickened glomerular basement membrane, and hyalinosis of arterioles. Functionally, however, the pathophysiology is reflected in dysfunction of the mesangium, the glomerular capillary wall, the tubulointerstitium, and the vasculature. For all diabetic patients, a comprehensive approach to management including glycemic and hypertensive control with RAASi combined with lipid control, dietary salt restriction, lowering of protein intake, increased physical activity, weight reduction, and smoking cessation can reduce the rate of progression of nephropathy and minimize the risk for cardiovascular events. This review focuses on the latest published data dealing with the mechanisms, diagnosis, and current treatment of DN.

Genetics of diabetes complications

Chronic hyperglycemia and duration of diabetes are the major risk factors associated with development of micro- and macrovascular complications of diabetes. Although it is believed that hyperglycemia induces damage to the particular cell subtypes, e.g., mesangial cells in the renal glomerulus, capillary endothelial cells in the retina, and neurons and Schwann cells in peripheral nerves, the exact mechanisms underlying these damaging defects are not yet well understood. Clustering of micro- and macrovascular complications in families of patients with diabetes suggests a strong genetic susceptibility. However, until now only a handful number of genetic variants were reported to be associated with either nephropathy (ACE, ELMO1, FRMD3, and AKR1B1) or retinopathy (VEGF, AKR1B1, and EPO), and only a few studies were carried out for genetic susceptibility to cardiovascular diseases (ADIPOQ, GLUL) in patients with diabetes. It is, therefore, obvious that the accumulation of more data from larger studies and better phenotypically characterized cohorts is needed to facilitate genetic discoveries and unravel novel insights into the pathogenesis of diabetic complications.

Diabetic kidney disease: from physiology to therapeutics

Diabetic kidney disease (DKD) defines the functional, structural and clinical abnormalities of the kidneys that are caused by diabetes. This complication has become the single most frequent cause of end-stage renal disease. The pathophysiology of DKD comprises the interaction of both genetic and environmental determinants that trigger a complex network of pathophysiological events, which leads to the damage of the glomerular filtration barrier, a highly specialized structure formed by the fenestrated endothelium, the glomerular basement membrane and the epithelial podocytes, that permits a highly selective ultrafiltration of the blood plasma. DKD evolves gradually over years through five progressive stages. Briefly they are: reversible glomerular hyperfiltration, normal glomerular filtration and normoalbuminuria, normal glomerular filtration and microalbuminuria, macroalbuminuria, and renal failure. Approximately 20-40% of diabetic patients develop microalbuminuria within 10-15 years of the diagnosis of diabetes, and about 80-90% of those with microalbuminuria progress to more advanced stages. Thus, after 15-20 years, macroalbuminuria occurs approximately in 20-40% of patients, and around half of them will present renal insufficiency within 5 years. The screening and early diagnosis of DKD is based on the measurement of urinary albumin excretion and the detection of microalbuminuria, the first clinical sign of DKD. The management of DKD is based on the general recommendations in the treatment of patients with diabetes, including optimal glycaemic and blood pressure control, adequate lipid management and abolishing smoking, in addition to the lowering of albuminuria.