Body Mass Index and Risk of Diabetic Nephropathy: A Mendelian Randomization Study

Association of Obesity With Kidney and Cardiac Outcomes Among Patients With Glomerular Disease: Findings From the Cure Glomerulonephropathy Network

RATIONALE & OBJECTIVE

The influence of obesity on cardiorenal outcomes in individuals with glomerular disease is incompletely known. This study examined the association between obesity and kidney and cardiovascular outcomes in children and adults with glomerular kidney disease.

STUDY DESIGN

Prospective, multicenter, observational study.

SETTING & PARTICIPANTS

Participants in the Cure Glomerulonephropathy Network (CureGN) who were≥5 years of age at enrollment.

EXPOSURE

Adult body mass index (BMI) groups: 20-24 (healthy) versus 25-34 (overweight/class 1 obesity) versus≥35 (class 2-3 obesity); and pediatric BMI percentiles: 5th-84th (healthy) versus 85th-94th (overweight) versus≥95th (obese).

OUTCOME

A composite kidney outcome (40% estimated glomerular filtration rate [eGFR] decline or kidney failure) and a composite cardiovascular outcome (myocardial infarction, stroke, heart failure, or death).

ANALYTICAL APPROACH

Time to composite primary outcomes by BMI strata were estimated using Kaplan-Meier analysis. The adjusted associations between BMI and outcomes were estimated using Cox proportional hazards analysis.

RESULTS

The study included 2,301 participants (1,548 adults and 753 children). The incidence of the primary kidney end point was 90.8 per 1,000 person-years in adults with class 2-3 obesity, compared with 58.0 in normal weight comparators. In the univariable analysis, class 2-3 obesity was associated with the primary kidney outcome only in adults (HR, 1.6 [95% CI, 1.1-2.2], P=0.006) compared with the healthy weight groups. In the multivariable adjusted analysis, class 2-3 obesity did not remain significant among adults when controlling for baseline eGFR and proteinuria. Adults with class 2-3 obesity had an incidence of 19.7 cardiovascular events per 1,000 person-years and greater cardiovascular risk (HR, 3.9 [95% CI, 1.4-10.7], P=0.009) in the fully adjusted model.

LIMITATIONS

BMI is an imperfect indicator of adiposity. Residual confounding may exist from socioeconomic factors.

CONCLUSIONS

Among adult patients in CureGN, class 2-3 obesity is associated with cardiovascular but not kidney outcomes when adjusted for potential confounding factors.

PLAIN-LANGUAGE SUMMARY

Obesity is a risk factor for adverse heart and kidney outcomes in patients with chronic kidney disease, but whether it is associated with these outcomes in patients with glomerulonephropathy is not known. This study used existing data from a large sample of adults and children with glomerular diseases to address this question. The findings suggest that obesity increases the risk of cardiovascular but not kidney disease events in adult patients with glomerular disease.

Causal relationships of lifestyle behaviours and body fat distribution on diabetic microvascular complications: a Mendelian randomization study

Objectives

To determine the causal correlations of lifestyle behaviours and body fat distribution on diabetic microvascular complications through a Mendelian Randomization (MR).

Methods

Genetic variants significantly associated with lifestyle behaviours, abdominal obesity, generalized obesity and diabetic microvascular complications were extracted from the UK Biobank (UKB) and FinnGen. The inverse variance weighted (IVW) method was regarded as the primary method. The main results were presented in odds ratio (OR) per standard deviation (SD) increase, and a series of sensitivity analyses were also conducted to validate the stability of the results.

Results

There was a positive causal correlation between smoking and the development of diabetic retinopathy (OR = 1.16; 95%CI: 1.04-1.30; p = 0.01). All of the indicators representing abdominal obesity had a statistically significant causal association with diabetic microvascular complications. Concerning generalized obesity, there were significant causal associations of body mass index (BMI) on diabetic nephropathy (OR = 1.92; 95%CI: 1.58-2.33; p < 0.001), diabetic retinopathy (OR = 1.27; 95%CI: 1.15-1.40; p < 0.001), and diabetic neuropathy (OR = 2.60; 95%CI: 1.95-3.45; p < 0.001). Other indicators including leg fat mass (left), and arm fat mass (left) also had a significant positive causality with diabetic microvascular complications.

Conclusion

Our findings suggested that smoking has a genetically causal association with the development of diabetic retinopathy rather than diabetic nephropathy and diabetic neuropathy. In addition, both abdominal obesity and generalized obesity are risk factors for diabetic microvascular complications. To note, abdominal obesity represented by waist circumference (WC) is the most significant risk factor.

Impaired Sensitivity to Thyroid Hormones Is Associated With the Change of Abdominal Fat in Euthyroid Type 2 Diabetes Patients: A Retrospective Cohort Study

Background and Aims: This study is aimed at investigating the potential correlation of thyroid hormone sensitivity with visceral fat area (VFA), subcutaneous fat area (SFA), and body mass index (BMI) among euthyroid type 2 diabetes mellitus (T2DM) subjects. Methods: Thyroid hormone sensitivity indices were calculated by thyroid feedback quantile-based index (TFQI), TSH index (TSHI), thyrotropin thyroxine resistance index (TT4RI), and free thyroxine (fT4)/free triiodothyronine (fT3) ratio. These indices were then categorized into quartiles for analysis. The outcomes were the change rates in VFA, SFA, and BMI among the participants. Result: The present study included 921 patients, with a median follow-up of 2.2 years. In multivariate linear regression, when compared to the first quartile, SFA demonstrated a notable decline in the fourth quartile of TFQI, TSHI, and TT4RI (β coefficient = -5.78, -7.83, and - 6.84 cm2 per year), while it significantly increased in the fourth quartile of fT4/fT3 ratio (β coefficient = 6.13 cm2 per year). Similarly, in the fourth quartile of TFQI, TSHI, and TT4RI, VFA decreased significantly, evidenced by β coefficients of -5.14, -4.80, and -4.08 cm2 per year. Yet, among the quartiles of the fT4/fT3 ratio, no discernible trend in VFA was observed. There was no significant association between indices of thyroid hormone sensitivity and change in BMI. Conclusion: Impaired central sensitivity to thyroid hormones was significantly associated with the reduction of VFA and SFA, while impaired peripheral sensitivity was associated with an increase of SFA in euthyroid individuals with T2DM.

Visceral adipose tissue and risk of diabetic nephropathy: A Mendelian randomization study

OBJECTIVE

Previous observational studies have established a correlation between visceral adipose tissue (VAT) and diabetic nephropathy (DN). However, the causality of this association remains unclear. Therefore, the aim of this study was to investigate the causal association between VAT and DN by employing two-sample Mendelian randomization (MR) methods.

METHODS

The primary MR approach employed was the random-effects inverse-variance weighted (IVW) method. Additionally, we employed alternative methods, including the weighted median (WM) approach, MR-Egger regression, and Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO). Sensitivity analyses were conducted to evaluate the robustness of the MR analyses.

RESULTS

Genetically predicted higher VAT mass was causally associated with a higher risk of DN. The results of the MR analyses were as follows: IVW(Beta = 0.948, odds ratio (OR) = 2.581, 95 % confidence interval (CI) = 2.100-3.173, p = 1.980e-19), WM (Beta = 1.126, OR = 3.082, 95 % CI = 2.278-4.171, p = 2.997e-13), MR-Egger (Beta = 1.315, OR = 3.724, 95 % CI = 1.981-6.998, p = 6.446e-05), and MR-PRESSO (Beta = 0.914, OR = 2.493, 95 % CI = 2.292-2.695, p = 3.121e-16). No pleiotropy was detected (p = 0.230).

CONCLUSIONS

This study provided genetic evidence that higher VAT mass was causally associated with a higher risk of DN.

Separating the effects of life course adiposity on diabetic nephropathy: a comprehensive multivariable Mendelian randomization study

Aims

Previous Mendelian randomization (MR) of obesity and diabetic nephropathy (DN) risk used small sample sizes or focused on a single adiposity metric. We explored the independent causal connection between obesity-related factors and DN risk using the most extensive GWAS summary data available, considering the distribution of adiposity across childhood and adulthood.

Methods

To evaluate the overall effect of each obesity-related exposure on DN (Ncase = 3,676, Ncontrol = 283,456), a two-sample univariate MR (UVMR) analysis was performed. The independent causal influence of each obesity-related feature on DN was estimated using multivariable MR (MVMR) when accounting for confounding variables. It was also used to examine the independent effects of adult and pediatric obesity, adjusting for their interrelationships. We used data from genome-wide association studies, including overall general (body mass index, BMI) and abdominal obesity (waist-to-hip ratio with and without adjustment for BMI, i.e., WHR and WHRadjBMI), along with childhood obesity (childhood BMI).

Results

UVMR revealed a significant association between adult BMI (OR=1.24, 95%CI=1.03-1.49, P=2.06×10-2) and pediatric BMI (OR=1.97, 95%CI=1.59-2.45, P=8.55×10-10) with DN risk. At the same time, adult WHR showed a marginally significant increase in DN (OR =1.27, 95%CI = 1.01-1.60, P=3.80×10-2). However, the outcomes were adverse when the influence of BMI was taken out of the WHR (WHRadjBMI). After adjusting for childhood BMI, the causal effects of adult BMI and adult abdominal obesity (WHR) on DN were significantly attenuated and became nonsignificant in MVMR models. In contrast, childhood BMI had a constant and robust independent effect on DN risk(adjusted for adult BMI: IVW, OR=1.90, 95% CI=1.60-2.25, P=2.03×10-13; LASSO, OR=1.91, 95% CI=1.65-2.21, P=3.80×10-18; adjusted for adult WHR: IVW, OR=1.80, 95% CI=1.40-2.31, P=4.20×10-6; LASSO, OR=1.90, 95% CI=1.56-2.32, P=2.76×10-10).

Interpretation

Our comprehensive analysis illustrated the hazard effect of obesity-related exposures for DN. In addition, we showed that childhood obesity plays a separate function in influencing the risk of DN and that the adverse effects of adult obesity (adult BMI and adult WHR) can be substantially attributed to it. Thus, several obesity-related traits deserve more attention and may become a new target for the prevention and treatment of DN and warrant further clinical investigation, especially in childhood obesity.

Association of BMI and waist circumference with diabetic microvascular complications: A prospective cohort study from the UK Biobank and Mendelian randomization analysis

AIMS

To investigate the precise association between BMI and waist circumference (WC) and diabetic complications, including retinopathy (DR), nephropathy (DN) and peripheral neuropathy (DPN).

METHODS

A multivariable-adjusted Cox proportional hazard model was used to evaluate the observed association from 30,541 UK Biobank participants with diabetes. A two-sample Mendelian randomization (MR) framework was applied to summary-level GWASs of BMI and WC comprising a total of 461,460 and 462,166 participants from UK Biobank to explore the potential causal association.

RESULTS

Higher BMI and WC were associated with increased risks of DR, DN, and DPN (HR (95% CI), per-SD increase: BMI: DR 1.09 (1.04-1.13), DN 1.37 (1.33-1.41), DPN 1.27 (1.20-1.34); WC: DR 1.11 (1.07-1.16), DN 1.41 (1.36-1.46), DPN 1.38 (1.30-1.45)) in the UK Biobank cohort. Univariate MR indicated that increased BMI and WC were causal risk factors for these complications (OR (95% CI), per-SD increase: BMI: DR 1.33 (1.22-1.45), DN 1.74 (1.47-2.07), DPN 2.20 (1.67-2.90); WC: DR 1.43 (1.27-1.61), DN 2.03 (1.62-2.55), DPN 2.80 (1.99-3.92)), and the effect sizes remained significant after adjustment for glycated hemoglobin.

CONCLUSIONS

Prospective observational and MR analyses provided evidence that high BMI and WC may represent potential causal risk factors for diabetic microvascular complications. Weight control might modify the risks of these complications independently of glycemic control and should be considered as a therapeutic recommendation.

Evaluation of Hepatic/Renal and Splenic/Renal Echointensity Ratio Using Ultrasonography in Diabetic Nephropathy

The objective of this study is to assess the hepatic/renal and splenic/renal echointensity ratios in ultrasonography in patients with and without diabetic nephropathy. This retrospective study included patients with diabetes mellitus who underwent ultrasound examinations at our hospital between January 2023 and May 2023. Ultrasound examinations were conducted using renal cortical echogenicity and corticomedullary differentiation by using B-mode ultrasonography. The hepatic/renal and splenic/renal echo intensity ratios were compared among study groups (diabetic patients with diabetic nephropathy and without nephropathy). The diabetic nephropathy group exhibited significantly higher right renal echointensity and left renal echointensity compared to the non-nephropathic group. Additionally, the splenic/renal echointensity ratio and hepatic/renal echointensity ratio were significantly lower in the diabetic nephropathy group. Urinary microalbumin levels were significantly correlated with right renal echointensity (r = 0.65, p < 0.001) and left renal echointensity (r = 0.69, p < 0.001). There was also a significant inverse correlation between the urinary albumin and splenic/renal echointensity ratio (r = -0.58, p < 0.001). Ultrasonography, specifically the assessment of hepatic/renal and splenic/renal echointensity ratios, shows promise as a noninvasive and cost-effective method for evaluating morphological changes in the kidneys in patients with diabetic nephropathy. These findings suggest that ultrasonography can be a valuable tool for monitoring the progression of diabetic nephropathy and contributing to its early detection and management.

Proteinuria, Body Mass Index, and the Risk of New-Onset Heart Failure: A Prospective Cohort Study in Northern China

Some studies have reported that body-mass index (BMI) and proteinuria are risk factors for heart failure (HF). However, the combined effect of BMI and proteinuria on HF is still unclear. We aimed to investigate the association of BMI and proteinuria levels with the risk of HF in a large community-based population. A total of 61, 113 individuals aged ≥18 years from the prospective Kailuan cohort (recruited during 2006-2007) without preexisting heart failure were included. Each participant was categorized into 4 groups according to BMI (< 25 kg/m² or ≥ 25 kg/m²) and the urine dipstick test results (negative or positive). The primary outcome was HF. We performed multivariable Cox regression analyses to identify the association between BMI and proteinuria category and incident HF. Over a mean follow-up of 9.97±0.75 years, a total of 987 individuals developed incident HF, 1.62 per 1000 person-years. Compared to BMI < 25 kg/m² and absence of proteinuria, the risk of HF was higher for BMI ≥ 25 kg/m² and positive proteinuria (HR 2.630, 95% CI 1.982-3.490, P < 0.0001) (P for trend < 0.0001). Degree of proteinuria in participants was associated with a significantly higher rate of incident HF in dose dependent manner. Compared to consistently negative proteinuria, the risk of HF increased by 75.0% (HR 1.750, 95% CI 1.368-2.239, P < 0.0001) and 127.0% (HR 2.270, 95% CI 1.540-3.347, P < 0.0001) in the proteinuria aggravated group and persistent positive group, respectively. Proteinuria combined with a high BMI level is associated with an increased risk for HF in the Chinese population. However, the mechanism is unknown and awaits further study.

Population attributable fractions of modifiable risk factors for microvascular complications of type 2 diabetes in China: An analysis using national cross-sectional data

AIM

To assess the population attributable fractions (PAFs) for modifiable risk factors for microvascular complications of type 2 diabetes (T2D) in China.

MATERIALS AND METHODS

Data collected from the China National HbA1c Surveillance System from 2009 to 2013 were used. The PAFs of four predefined risk factors, including an HbA1c of 7% or higher, blood pressure (BP) of 130/80 mmHg or higher, low-density lipoprotein-cholesterol (LDL-C) of 1.8 mmol/L or higher and body mass index (BMI) of 24 kg/m² or higher, were calculated for diabetic microvascular complications, including diabetic retinopathy (DR), diabetic kidney disease (DKD) and distal symmetric polyneuropathy (DSPN). PAFs were further adjusted for age, sex and duration of diabetes.

RESULTS

In total, there were 998 379 participants with T2D from nationwide mainland China included in this analysis. As for DR, an HbA1c of 7% or higher, BP of 130/80 mmHg or higher, LDL-C of 1.8 mmol/L or higher and BMI of 24 kg/m² or higher conferred PAFs of 16.2%, 15.2%, 5.8% and 2.8%, respectively. In the case of DKD, BP of 130/80 mmHg or higher provided a PAF of 25.2%, followed by an HbA1c of 7% or higher (13.9%), BMI of 24 kg/m² or higher (8.0%) and LDL-C of 1.8 mmol/L or higher (5.6%). As for DSPN, an HbA1c of 7% or higher, BP of 130/80 mmHg or higher, LDL-C of 1.8 mmol/L or higher and BMI of 24 kg/m² or higher contributed to PAFs of 14.2%, 11.7%, 5.9% and 5.8%, respectively. PAFs for diabetic microvascular complications were mildly to moderately reduced after adjusting for participants' age, sex and duration of diabetes.

CONCLUSIONS

Suboptimal glycaemic and BP control were the main contributors to diabetic microvascular complications, while the PAFs of unmet LDL-C and BMI control targets were quite limited for diabetic microvascular complications. In addition to glycaemic control, BP control should be especially prioritized in the management of diabetic microvascular complications to further reduce the disease burden.

Advancing a causal role of type 2 diabetes and its components in developing macro- and microvascular complications via genetic studies

The role of diabetes in developing microvascular and macrovascular complications has been subject to extensive research. Despite multiple observational and genetic studies, the causal inference of diabetes (and associated risk factors) on those complications remains incomplete. In this review, we focused on type 2 diabetes, as the major form of diabetes, and investigated the evidence of causality provided by observational and genetic studies. We found that genetic studies based on Mendelian randomization provided consistent evidence of causal inference of type 2 diabetes on macrovascular complications; however, the evidence for causal inference on microvascular complications has been somewhat limited. We also noted high BMI could be causal for several diabetes complications, notable given high BMI is commonly upstream of type 2 diabetes and the recent calls to target weight loss more aggressively. We emphasize the need for further studies to identify type 2 diabetes components that mostly drive the risk of those complications. Even so, the genetic evidence summarized broadly concurs with the need for a multifactorial risk reduction approach in type 2 diabetes, including addressing excess adiposity.