Microalbuminuria is associated with insulin resistance in nondiabetic subjects: the insulin resistance atherosclerosis study

A Population-Based Study of the Mediating Role of WBC, NEUT and PLT in the Relationship Between Triglyceride-Glucose Index and Urinary Albumin Excretion

Aim

To assess the potential association between the TyG index and the risk of abnormal UACR. Additionally, we aimed to determine the role and degree of influence of inflammatory biomarkers between the TyG index and abnormal UACR.

Materials and Methods

A cross-sectional study recruited 1021 participants from a health management center between 2021 and 2022. Logistic or linear regression models, as well as mediation analysis, were employed to investigate the associations between the TyG index, inflammatory biomarkers (total and differential white blood cell counts, platelet, mean platelet volume(MPV), C-reactive protein(CRP)), and the risk of abnormal UACR.

Results

The study included 1021 participants, of whom 55.0% were men. The median age (interquartile range [IQR]) was 61.0 (53, 70) years. In multivariable-adjusted logistic regression models, both with and without the inclusion of smoking, alcohol drinking, BMI, Lipid-lowering drugs using, TC, SUA, ALT, and AST as potential covariates, the TyG index was associated with the risk of UACR, both with the odds ratios (ORs) per 1-standard deviation (SD) increase were 1.32 (95% CI, 1.08-1.62) and 1.27 (95% CI, 1.05-1.52), respectively. This study also demonstrated a significant indirect effect of the TyG index on the risk of abnormal UACR through total white blood cell counts, neutrophil counts and platelet (P values < 0.05); The proportions mediated was 11.2%, 3.5% and 29.6% for each respective variable.

Conclusion

Insulin resistance and inflammation are associated with an increased risk of kidney insufficiency. And indicators of inflammation weakly mediate insulin resistance and risk of kidney insufficiency.

Association between insulin resistance and vascular damage in an adult population in China: a cross-sectional study

There is a relative scarcity of large-scale population studies investigating the relationship between the insulin resistance index of homeostasis model assessment (HOMA-IR) and vascular damage. Therefore, we assessed the association between HOMA-IR and vascular damage in adults aged 18 years and older in China. A total of 17,985 research subjects were included. Vascular damage markers and relevant laboratory tests were measured. HOMA-IR was calculated as (fasting insulin * fasting blood glucose)/22.5. Vascular damage included arteriosclerosis (ba-PWV > 1800 cm/s), peripheral artery disease (ABI < 0.9), and microalbuminuria (UACR > 30 mg/g). The relationship between HOMA-IR and vascular damage was analyzed using the RCS. The restricted cubic spline (RCS) analysis suggested that HOMA-IR was nonlinearly associated with arteriosclerosis (P for no-liner < 0.01), peripheral artery disease (P for no-liner < 0.01), and microalbuminuria (P for no-liner < 0.01). Further segmented regression analyses revealed that in study subjects with HOMA-IR < 5, we found that HOMA-IR was associated with an increased OR for arteriosclerosis (OR: 1.36, 95% CI (1.28, 1.45), P < 0.01), peripheral artery disease (OR: 1.33, 95% CI (1.10, 1.60), P < 0.01) and microalbuminuria (OR: 1.59, 95% CI (1.49, 1.70), P < 0.01). HOMA-IR is an independent risk factor for vascular damage, both macrovascular and microvascular. The phenomenon of saturation of HOMA-IR with vascular damage needs further investigation.

Cardiometabolic comorbidities and complications of obesity and chronic kidney disease (CKD)

Obesity and chronic kidney disease are two ongoing progressive clinical pandemics of major public health and clinical care significance. Because of their growing prevalence, chronic indolent course and consequent complications both these conditions place significant burden on the health care delivery system especially in developed countries like the United States. Beyond the chance coexistence of both of these conditions in the same patient based on high prevalence it is now apparent that obesity is associated with and likely has a direct causal role in the onset, progression and severity of chronic kidney disease. The causes and underlying pathophysiology of this are myriad, complicated and multi-faceted. In this review, continuing the theme of this special edition of the journal on " The Cross roads between Endocrinology and Nephrology" we review the epidemiology of obesity related chronic kidney disease (ORCKD), and its various underlying causes and pathophysiology. In addition, we delve into the consequent comorbidities and complications associated with ORCKD with particular emphasis on the cardio metabolic consequences and then review the current body of evidence for available strategies for chronic kidney disease modulation in ORCKD as well as the potential unique role of weight reduction and management strategies in its improvement and risk reduction.

Correlation between the triglyceride-glucose index and chronic kidney disease among adults with metabolic-associated fatty liver disease: fourteen-year follow-up

BACKGROUND AND AIMS

According to previous studies, triglyceride-glucose (TyG) is related to chronic kidney disease (CKD), but no studies have explored the correlation between TyG and CKD among adults with metabolic dysfunction-associated fatty liver disease (MAFLD). We aimed to explore the associations of the TyG index with CKD among adults with MAFLD.

METHODS

In this retrospective observational cohort study, data from 11,860 participants who underwent a minimum of three health assessments between 2008 and 2015 were retrospectively collected. Participants were followed up until the final medical visit or health examination. CKD refers to an eGFR < 60 mL/min per 1·73 m2 or the occurrence of two or more incidents of proteinuria.

RESULTS

Within a median 10·02-year follow-up period, 2005 (16·9%) participants reported developing CKD. Multivariate Cox regression models indicated a noticeable correlation between the TyG index and CKD incidence (HR per unit increase, 1.19; 95% CI: 1.09-1.29) and between the TyG index and CKD incidence (HR per SD increase, 1.12; 95% CI: 1.06-1.18). The CKD incidence increased by 1.8 times in participants in the highest TyG index quartile relative to patients in the lowest quartile of the TyG index quartile (HR 1·18, 95% CI: 1.01-1.38, P = 0.007). According to subgroup analysis, an elevated TyG index is likely to become more harmful to participants younger than 60 years (P for interaction = 0.035).

CONCLUSION

An elevated TyG index may increase CKD incidence among MAFLD adults, particularly among younger people. Early intervention may help reduce the incidence of CKD.

Changes in proteinuria and the associated risks of ischemic heart disease, acute myocardial infarction, and angina pectoris in Korean population

OBJECTIVES

Proteinuria is widely used to predict cardiovascular risk. However, there is insufficient evidence to predict how changes in proteinuria may affect the incidence of cardiovascular disease.

METHODS

The study included 265,236 Korean adults who underwent health checkups in 2003-2004 and 2007-2008. They were categorized into 4 groups based on changes in proteinuria (negative: negative → negative; resolved: proteinuria ≥1+ → negative; incident: negative → proteinuria ≥1+; persistent: proteinuria ≥1+ → proteinuria ≥1+). We conducted 6 years of follow-up to identify the risks of developing ischemic heart disease (IHD), acute myocardial infarction (AMI), and angina pectoris according to changes in proteinuria. A multivariate Cox proportional-hazards model was used to calculate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for incident IHD, AMI, and angina pectoris.

RESULTS

The IHD risk (expressed as HR [95% CI]) was the highest for persistent proteinuria, followed in descending order by incident and resolved proteinuria, compared with negative proteinuria (negative: reference, resolved: 1.211 [95% CI, 1.104 to 1.329], incident: 1.288 [95% CI, 1.184 to 1.400], and persistent: 1.578 [95% CI, 1.324 to 1.881]). The same pattern was associated with AMI (negative: reference, resolved: 1.401 [95% CI, 1.048 to 1.872], incident: 1.606 [95% CI, 1.268 to 2.035], and persistent: 2.069 [95% CI, 1.281 to 3.342]) and angina pectoris (negative: reference, resolved: 1.184 [95% CI, 1.065 to 1.316], incident: 1.275 [95% CI, 1.160 to 1.401], and persistent: 1.554 [95% CI, 1.272 to 1.899]).

CONCLUSIONS

Experiencing proteinuria increased the risks of IHD, AMI, and angina pectoris even after proteinuria resolved.

Determinants and prognostic value of albuminuria in adult patients with congenital heart disease

BACKGROUND

The determinants and prognostic value of albuminuria remain unclear in patients with adult congenital heart disease (ACHD), especially in those with Fontan circulation (FC).

METHODS

We retrospectively reviewed 512 consecutive ACHD patients and investigated the determinants of urinary albumin-to-creatinine ratio (ACR) and albuminuria (MAU) and their association with all-cause mortality. Demographic data and laboratory and hemodynamic parameters were collected. Regression analysis and Cox proportional hazard models were used to identify the relationship between log ACR and variables, and clinical factors and all-cause mortality, respectively.

RESULTS

Body mass index, aortic systolic blood pressure (ASP), arterial oxygen saturation (SaO2), glycated hemoglobin (HbA1c), B-type natriuretic peptide, and diuretic use were independently associated with log ACR. ASP, SaO2, and HbA1c were independently associated with MAU (P < .05-0.001). The prevalence of MAU was highest in unrepaired patients with low SaO2 (50%; P < .0001). Log ACR and MAU were associated with exercise capacity and all-cause mortality (P < .0001 for both) independent of renal function. Patients with ACHD, MAU, and renal dysfunction (n = 23) had the highest risk of all-cause mortality, while those without MAU or renal dysfunction had the lowest risk (P < .0001). These prognostic values remained significant in separate analyses of Fontan and biventricular circulation (P < .0001).

CONCLUSIONS

ASP, SaO2, and HbA1c levels were independently associated with MAU in ACHD patients. MAU and log ACR were associated with all-cause mortality in patients with Fontan and biventricular circulation, independent of renal dysfunction.

Kidney Considerations in Pediatric Obesity

PURPOSE OF REVIEW

Chronic kidney disease (CKD) is a common condition and a major cause of morbidity and mortality in adults, but children and adolescents are also at risk for early kidney injury and development of CKD. Obesity contributes both directly and indirectly to the development of CKD. The purpose of this review is to describe obesity-related kidney disease (ORKD) and diabetic kidney disease (DKD) and their impact in the pediatric population.

RECENT FINDINGS

Although obesity-related CKD in childhood and adolescence is uncommon, nascent kidney damage may magnify the lifetime risk of CKD. Glomerular hyperfiltration is an early phenotype of both ORKD and DKD and typically manifests prior to albuminuria and progressive decline in GFR. Novel treatments for obesity and type 2 diabetes exerting protective effects on the kidneys are being investigated for use in the pediatric population. It is important to understand the impact of obesity on the kidneys more fully in the pediatric population to help detect injury earlier and intervene prior to the onset of irreversible progression of disease and to guide future research in this area.

The Associations between Kidney Function and Sexual Dysfunction among Males and Females with Type 2 Diabetes Mellitus

Background and Objectives: Diabetic kidney disease (DKD), expressed either as albuminuria, low estimated glomerular filtration rate (eGFR) or both, and sexual dysfunction (SD), are common complications among type 2 diabetes mellitus (T2DM) patients. This study aims to assess whether an association exists between DKD and SD, erectile dysfunction (ED) or female sexual dysfunction (FSD) in a T2DM population. Materials and Methods: A cross-sectional study was designed and conducted among T2DM patients. The presence of SD was assessed using the International Index of Erectile Function and the Female Sexual Function Index questionnaires for males and females, respectively, and patients were evaluated for DKD. Results: Overall, 80 patients, 50 males and 30 females, agreed to participate. Sexual dysfunction was present in 80% of the study population. Among the participants, 45% had DKD, 38.5% had albuminuria and/or proteinuria and 24.1% had an eGFR below 60 mL/min/1.73 m². The eGFR was associated with SD, ED and FSD. Moreover, SD and ED were proven as significant determinants for lower eGFR values in multiple linear regression analyses. DKD was associated with lower lubrication scores and eGFR was associated with lower desire, arousal, lubrication and total scores; however, the multivariate linear regression analyses showed no significant associations between them. Older age resulted in significantly lower arousal, lubrication, orgasm and total FSFI scores. Conclusions: SD is commonly encountered in older T2DM patients and DKD affects almost half of them. The eGFR has been significantly associated with SD, ED and FSD, while SD and ED were proven to be significant determinants for the eGFR levels.

Non-insulin-based insulin resistance indices for predicting all-cause mortality and renal outcomes in patients with stage 1-4 chronic kidney disease: another paradox

Non-insulin-based insulin resistance (IR) indices serve as the indicators of metabolic syndrome (MetS) but have limited value for predicting clinical outcomes. Whether the obesity paradox affects the predictive value of these indicators in patients with chronic kidney disease (CKD) remains unknown. We investigated whether MetS and non-insulin-based IR indices can predict all-cause mortality and renal outcomes in a prospective observational study with stage 1-4 CKD Asians (N = 2,457). These IR indices were associated with MetS. A Cox regression model including body mass index (BMI) revealed an association between MetS and renal outcomes. Among the IR indices, only high triglyceride-glucose (TyG) index was associated with adverse renal outcomes: the hazard ratio of Q4 quartile of the TyG index was 1.38 (1.12-1.70). All-cause mortality was marginally associated with MetS but not high IR indices. Low TyG and TyG-BMI indices as well as low BMI and triglyceride were paradoxically associated with increased risks of clinical outcomes. The triglyceride-to-high-density lipoprotein cholesterol ratio and metabolic score for IR indices were not associated with clinical outcomes. In conclusion, MetS and TyG index predict renal outcome and obesity paradox affects the prediction of IR indices in patients with stage 1-4 CKD.

Elevated urine albumin-to-creatinine ratio increases the risk of new-onset heart failure in patients with type 2 diabetes

BACKGROUND

Although albuminuria has been linked to heart failure in the general population, the relationship between urine albumin-to-creatinine ratio (uACR) and heart failure in type 2 diabetes patients is not well understood. We aimed to investigate the relationship between uACR and new-onset heart failure (HF) in type 2 diabetics.

METHODS

We included 9287 Chinese participants with type 2 diabetes (T2D) but no heart failure (HF) who were assessed with uACR between 2014 and 2016. The participants were divided into three groups based on their baseline uACR: normal (< 3 mg/mmol), microalbuminuria (3-30 mg/mmol), and macroalbuminuria (≥ 30 mg/mmol). The relationship between uACR and new-onset HF was studied using Cox proportional hazard models and restricted cubic spline. The area under the receiver operating characteristic curve (AUC), net reclassification improvement (NRI), and integrated discrimination improvement (IDI) were used to see if incorporating uACR into existing models could improve performance.

RESULTS

216 new-onset HF cases (2.33%) were recorded after a median follow-up of 4.05 years. When compared to normal uACR, elevated uACR was associated with a progressively increased risk of new-onset HF, ranging from microalbuminuria (adjusted HR, 2.21; 95% CI 1.59-3.06) to macroalbuminuria (adjusted HR, 6.02; 95% CI 4.11-8.80), and 1 standard deviation (SD) in ln (uACR) (adjusted HR, 1.89; 95% CI 1.68-2.13). The results were consistent across sex, estimated glomerular filtration rate, systolic blood pressure, and glycosylated hemoglobin subgroups. The addition of uACR to established HF risk models improved the HF risk prediction efficacy.

CONCLUSIONS

Increasing uACR, even below the normal range, is an independent risk factor for new-onset HF in a type 2 diabetic population. Furthermore, uACR may improve HF risk prediction in community-based T2D patients.

Is There Any Association Between Triglyceride-Glucose Index and Graft Function in Kidney Transplant Recipients?

BACKGROUND

Although previous studies have illustrated the relationship between chronic kidney disease, coronary artery disease, erectile dysfunction, and the triglyceride-glucose index (TyGi), the relationship between this index and postoperative graft function in patients undergoing renal transplantation has yet to be investigated. In the present study, we aimed to reveal the association between the TyGi and renal graft outcomes in patients who underwent renal transplantation.

METHODS

We retrospectively collected data on living and cadaveric kidney donor recipients between May 2019 and April 2022. The recipients' age, sex, body mass index, preoperative fasting glucose and triglyceride levels, TyGi, estimated glomerular filtration rate (eGFR), and serum creatinine measurement data were recorded. The patients were divided into 2 groups according to their GFR values (group 1: GFR <60 mL/min/1.73 m²; group 2: GFR ≥60 mL/min/1.73 m²). Follow-up serum creatinine-eGFR levels and TyGi measurements were compared between the recipients in group 1 and group 2.

RESULTS

The mean TyGi measurements of the recipients were 8.79 ± 0.64 in group 1 and 8.83 ± 0.72 in group 2. There was no statistically significant difference in terms of the TyGi measurements between the 2 groups (P >. 05). No statistically significant correlation was found between the recipients' creatinine, eGFR, and TyGi at 1st, 6th, and 12th postoperative months (P > .05).

CONCLUSIONS

We believe that the relationship between the TyGi and renal graft function can be more clearly understood in prospective studies that include a higher number of patients and a longer follow-up period.

Obesity and chronic kidney disease

The prevalence of obesity has increased dramatically during the past decades, which has been a major health problem. Since 1975, the number of people with obesity worldwide has nearly tripled. An increasing number of studies find obesity as a driver of chronic kidney disease (CKD) progression, and the mechanisms are complex and include hemodynamic changes, inflammation, oxidative stress, and activation of the renin-angiotensin-aldosterone system (RAAS). Obesity-related kidney disease is characterized by glomerulomegaly, which is often accompanied by localized and segmental glomerulosclerosis lesions. In these patients, the early symptoms are atypical, with microproteinuria being the main clinical manifestation and nephrotic syndrome being rare. Weight loss and RAAS blockers have a protective effect on obesity-related CKD, but even so, a significant proportion of patients eventually progress to end-stage renal disease despite treatment. Thus, it is critical to comprehend the mechanisms underlying obesity-related CKD to create new tactics for slowing or stopping disease progression. In this review, we summarize current knowledge on the mechanisms of obesity-related kidney disease, its pathological changes, and future perspectives on its treatment.

Development and Validation of an Insulin Resistance Model for a Population with Chronic Kidney Disease Using a Machine Learning Approach

Background: Chronic kidney disease (CKD) is a complex syndrome without a definitive treatment. For these patients, insulin resistance (IR) is associated with worse renal and patient outcomes. Until now, no predictive model using machine learning (ML) has been reported on IR in CKD patients. Methods: The CKD population studied was based on results from the National Health and Nutrition Examination Survey (NHANES) of the USA from 1999 to 2012. The homeostasis model assessment of IR (HOMA-IR) was used to assess insulin resistance. We began the model building process via the ML algorithm (random forest (RF), eXtreme Gradient Boosting (XGboost), logistic regression algorithms, and deep neural learning (DNN)). We compared different receiver operating characteristic (ROC) curves from different algorithms. Finally, we used SHAP values (SHapley Additive exPlanations) to explain how the different ML models worked. Results: In this study population, 71,916 participants were enrolled. Finally, we analyzed 1,229 of these participants. Their data were segregated into the IR group (HOMA IR > 3, n = 572) or non-IR group (HOMR IR ≤ 3, n = 657). In the validation group, RF had a higher accuracy (0.77), specificity (0.81), PPV (0.77), and NPV (0.77). In the test group, XGboost had a higher AUC of ROC (0.78). In addition, XGBoost also had a higher accuracy (0.7) and NPV (0.71). RF had a higher accuracy (0.7), specificity (0.78), and PPV (0.7). In the RF algorithm, the body mass index had a much larger impact on IR (0.1654), followed by triglyceride (0.0117), the daily calorie intake (0.0602), blood HDL value (0.0587), and age (0.0446). As for the SHAP value, in the RF algorithm, almost all features were well separated to show a positive or negative association with IR. Conclusion: This was the first study using ML to predict IR in patients with CKD. Our results showed that the RF algorithm had the best AUC of ROC and the best SHAP value differentiation. This was also the first study that included both macronutrients and micronutrients. We concluded that ML algorithms, particularly RF, can help determine risk factors and predict IR in patients with CKD.

The Association of Excess Body Weight with Risk of ESKD Is Mediated Through Insulin Resistance, Hypertension, and Hyperuricemia

BACKGROUND

Insulin resistance, hypertension, hyperuricemia, and hypercholesterolemia are hypothesized to be important intermediates in the relationship between excess body weight and CKD risk. However, the magnitude of the total effect of excess body weight on ESKD mediated through these four pathways remains to be quantified.

METHODS

We applied a model for analysis of correlated mediators to population-based data from 100,269 Austrian individuals (mean age 46.4 years). Association of body mass index (BMI) was coalesced with ESKD risk into direct association. Indirect associations were mediated through the triglyceride-glucose (TyG) index (as an indicator of insulin resistance), mean arterial pressure (MAP), uric acid (UA), and total cholesterol (TC).

RESULTS

Mean follow-up was 23.1 years with 463 (0.5%) incident ESKD cases. An unhealthy metabolic profile (prevalence 32.4%) was associated with a markedly increased ESKD risk (multivariably adjusted hazard ratio (aHR), 3.57; 95% CI, 2.89 to 4.40), independent of BMI. A 5-kg/m2 higher BMI was associated with a 57% increased ESKD risk (aHRtotal association, 1.57; 1.38 to 1.77). Of this association, 99% (76% to 140%) arose from all mediators jointly; 33% (22% to 49%) through TyG index; 34% (24% to 50%) through MAP; 30% (21% to 45%) through UA; and 2% (-1% to 4%) through TC. The remaining direct association was nonsignificant (aHRdirect association, 1.01; 0.88 to 1.14).

CONCLUSIONS

TyG index, MAP, and UA, but not TC, mediate the association of BMI with ESKD in middle-aged adults. Our findings highlight that in addition to weight reduction, the control of metabolic risk factors might be essential in mitigating the adverse effects of BMI on kidney function.

Obesity-related glomerulopathy: Current approaches and future perspectives

Obesity-related glomerulopathy (ORG) is a silent comorbidity which is increasing in incidence as the obesity epidemic escalates. ORG is associated with serious health consequences including chronic kidney disease, end-stage renal disease (ESRD), and increased mortality. Although the pathogenic mechanisms involved in the development of ORG are not fully understood, glomerular hemodynamic changes, renin-angiotensin-aldosterone system (RAAS) overactivation, insulin-resistance, inflammation and ectopic lipid accumulation seem to play a major role. Despite albuminuria being commonly used for the non-invasive evaluation of ORG, promising biomarkers of early kidney injury that are emerging, as well as new approaches with proteomics and metabolomics, might permit an earlier diagnosis of this disease. In addition, the assessment of ectopic kidney fat by renal imaging could be a useful tool to detect and evaluate the progression of ORG. Weight loss interventions appear to be effective in ORG, although large-scale trials are needed. RAAS blockade has a renoprotective effect in patients with ORG, but even so, a significant proportion of patients with ORG will eventually progress to ESRD despite therapeutic efforts. It is noteworthy that certain antidiabetic agents such as sodium-glucose cotransporter 2 inhibitors (SGLT2i) or glucagon-like peptide-1 receptor agonists (GLP-1 RAs) could be useful in the treatment of ORG through different pleiotropic effects. In this article, we review current approaches and future perspectives in the care and treatment of ORG.

Impaired fasting blood glucose is associated with incident albuminuria: Data from a Chinese community-based cohort

OBJECTIVE

Growing evidence links hyperglycemia in the diabetic range to albuminuria, while the association between impaired fasting glucose (IFG) and albuminuria is not well established. The study intends to explore whether IFG is longitudinally associated with incident albuminuria in a non-diabetic Chinese community-based cohort.

METHODS

Participants with urine albumin creatinine ratio (UACR) both in 2014 and 2018 from the atherosclerotic cohort were included. A total of 1649 non-diabetic subjects were ultimately included in the analysis after ruling out participants with UACR≥30 mg/g and self-reported history of renal diseases at baseline. Fasting blood glucose (FBG) was assessed by Roche C8000 Automatic Analyzer and UACR was measured with Unicel DxC 800 Synchron biochemistry analyzer using spot morning urine sample. Incident albuminuria was defined as an advance from normal to microalbuminuria or macroalbuminuria. Multivariable logistic regression model was used to investigate the relationship between FBG and incident albuminuria.

RESULTS

During a mean follow-up of 4.38 years, 82 (4.97%) participants developed incident albuminuria. Logistic regression analysis showed that after adjustment, the risk of incident albuminuria increased by 71% (OR = 1.71, 95%CI: 1.11-2.62, P = 0.014) for every 18 mg/dl (1 mmol/l) increase of FBG level. Besides, FBG level was independently and gradably associated with incident albuminuria. Compared with the FBG < 100 mg/dl (5.6 mmol/l) group, the risk increased 1.63-fold for incident albuminuria (OR = 2.63, 95%CI:1.42-4.87, P = 0.002) in the FBG 110-126 mg/dl (6.1-7.0 mmol/l) group while the association between FBG 100-110 mg/dl (5.6-6.1 mmol/l) group and the outcome was not significant. Subgroup and interaction analyses were performed and no significant modification effect was found.

CONCLUSION

IFG was independently associated with incident albuminuria in Chinese community-based population. The higher the FBG level, the higher the risk of incident albuminuria, which may suggest that screening for albuminuria should be emphasized in population with IFG so as to prevent and treat it in an early stage.

Insulin Resistance is Associated with Clinical Manifestations of Diabetic Kidney Disease (Glomerular Hyperfiltration, Albuminuria, and Kidney Function Decline)

Clinical features of diabetic kidney disease include glomerular hyperfiltration, albuminuria, and kidney function decline towards End-Stage Kidney Disease (ESKD). There are presently neither specific markers of kidney involvement in patients with diabetes nor strong predictors of rapid progression to ESKD. Serum-creatinine-based equations used to estimate glomerular filtration rate are notoriously unreliable in patients with diabetes. Early kidney function decline, reduced glomerular filtration rate, and proteinuria contribute to identifying diabetic patients at higher risk for rapid kidney function decline. Unlike proteinuria, the elevation of urinary albumin excretion in the range of microalbuminuria is frequently transient in patients with diabetes and does not always predict progression towards ESKD. Although the rate of progression of kidney function decline is usually accelerated in the presence of proteinuria, histological lesions of diabetes and ESKD may occur with normal urinary albumin excretion. No substantial reduction in the rate of ESKD associated with diabetes has been observed during the last decades despite intensified glycemic control and reno-protective strategies, indicating that existing therapies do not target underlying pathogenic mechanisms of kidney function decline. Very long-term effects of sodium-glucose transporters- 2 inhibitors and glucagon-like peptide-1 analogs remain to be defined. In patients with diabetes, glucagon secretion is typically elevated and induces insulin resistance. Insulin resistance is consistently and strongly associated with clinical manifestations of diabetic kidney disease, suggesting that reduced insulin sensitivity participates in the pathogenesis of the disease and may represent a therapeutic objective. Amelioration of insulin sensitivity in patients with diabetes is associated with cardioprotective and kidney-protective effects.

The association of glucose metabolism and kidney function in middle-aged adults

BACKGROUND

Previous clinical studies have shown that various measures of glucose metabolism are associated with a risk of chronic kidney disease in different populations, but results were not consistent. In this study we assessed measures of glucose metabolism and their association with kidney function in a population-based study.

METHODS

The Netherlands Epidemiology of Obesity study is a population-based cohort study of middle-aged men and women. We categorized the study population according to glycaemic levels into normoglycaemia (reference group), pre-diabetes mellitus (pre-DM), known DM and newly diagnosed DM. Outcome variables were serum creatinine, estimated glomerular filtration rate (eGFR), glomerular hyperfiltration (defined as an eGFR >90th percentile; >102 mL/min/1.73 m2) and micro-albuminuria. We examined the association between measures of glucose metabolism [fasting glucose, haemoglobin A1c (HbA1c), fasting insulin, glucose area under the curve (AUC), insulin AUC, Homoeostatic Model Assessment of Insulin Resistance (HOMA-IR), HOMA of β-cell function (HOMA-B) and disposition index] and measures of kidney function.

RESULTS

Of the total population (N = 6338), 55% of participants were classified as normoglycaemic (reference), 35% as pre-DM, 7% as DM and 4% as newly diagnosed DM. Compared with the reference group, diagnosed and newly diagnosed DMs were associated with a slightly higher trend in eGFR {+2.1 mL/min/1.73 m2 [95% confidence interval (CI) -0.2-4.4] and +2.7 mL/min/1.73 m2 [95% CI -0.3-5.7], respectively}. A 1% higher HbA1c was associated with increased odds of hyperfiltration [odds ratio (OR) 1.41 (95% CI 1.06-1.88)]. Higher levels of fasting plasma glucose, AUC glucose and HOMA-B were associated with hyperfiltration. Fasting insulin, AUC insulin and HOMA-IR were not associated with hyperfiltration. The OR of microalbuminuria was 1.21 (95% CI 1.04-1.42) per mmol/L higher fasting glucose concentrations.

CONCLUSIONS

Both fasting and post-prandial glucose and HOMA-B, but not measures of insulin resistance, were associated with glomerular hyperfiltration, while fasting glucose was also associated with microalbuminuria.

Increased risk for microvascular complications among women with gestational diabetes in the third trimester

AIMS

The risk of microvascular disease has been thought to commence with the onset of overt diabetes. Women with gestational diabetes have only had a short-term exposure to frank hyperglycemia, but, due to underlying β-cell dysfunction, they may also have had long-term exposure to mild degrees of hyperglycemia. The aim of the study was to determine whether women with gestational diabetes are at increased risk for microalbuminuria and retinopathy compared to women with normal glucose tolerance in pregnancy.

METHODS

We recruited women aged ≥ 25 years with singleton pregnancies at 32 to 40 weeks' gestational age, with and without gestational diabetes. Women with hypertension, preeclampsia, or pre-gestational diabetes were excluded.

RESULTS

Of 372 women included in the study, 195 had gestational diabetes. The prevalence of microalbuminuria was 15% among those with gestational diabetes versus 6% in those with normal glucose tolerance (adjusted odds ratio 2.4, 95% confidence interval 1.1 to 5.2, p = 0.006). Diastolic blood pressure and HbA1c were associated with microalbuminuria. The prevalence of retinopathy did not differ between groups (10% versus 11%).

CONCLUSIONS

Women with gestational diabetes have an increased risk of microalbuminuria in the third trimester, despite having been exposed to only a brief period of overt hyperglycemia.

Insulin resistance in glomerular podocytes: Potential mechanisms of induction

Glomerular podocytes are a target for the actions of insulin. Accumulating evidence indicates that exposure to nutrient overload induces insulin resistance in these cells, manifested by abolition of the stimulatory effect of insulin on glucose uptake. Numerous recent studies have investigated potential mechanisms of the induction of insulin resistance in podocytes. High glucose concentrations stimulated reactive oxygen species production through NADPH oxidase activation, decreased adenosine monophosphate-activated protein kinase (AMPK) phosphorylation, and reduced deacetylase sirtuin 1 (SIRT1) protein levels and activity. Calcium signaling involving transient receptor potential cation channel C, member 6 (TRPC6) also was demonstrated to play an essential role in the regulation of insulin-dependent signaling and glucose uptake in podocytes. Furthermore, podocytes exposed to diabetic environment, with elevated insulin levels become insulin resistant as a result of degradation of insulin receptor (IR), resulting in attenuation of insulin signaling responsiveness. Also elevated levels of palmitic acid appear to be an important factor and contributor to podocytes insulin resistance. This review summarizes cellular and molecular alterations that contribute to the development of insulin resistance in glomerular podocytes.

The Triglyceride-Glucose Index and Obesity-Related Risk of End-Stage Kidney Disease in Austrian Adults

IMPORTANCE

It is unknown whether the triglyceride-glucose (TyG) index as a measure of insulin resistance is associated with the risk of developing end-stage kidney disease (ESKD). Because individuals who are overweight or obese often develop insulin resistance, mediation of the association between body mass index (BMI) and ESKD risk through the TyG index seems plausible but has not been investigated.

OBJECTIVE

To evaluate whether the TyG index is associated with ESKD risk and, if so, to what extent the TyG index mediates the association between BMI and ESKD.

DESIGN, SETTING, AND PARTICIPANTS

A total of 176 420 individuals were recruited during routine health examinations to participate in the Austrian Vorarlberg Health Monitoring and Promotion Program (VHM&PP), a prospective, population-based cohort study with participant enrollment between January 1, 1988, and June 30, 2005, and a mean follow-up of 22.7 years. Data analysis was conducted from March 1, 2020, to September 30, 2020.

EXPOSURES

Body mass index and the logarithmized product of fasting triglyceride and glucose concentrations (TyG index), as determined during the baseline health examination.

MAIN OUTCOMES AND MEASURES

End-stage kidney disease, as indicated by initiation of kidney replacement therapy, either dialysis or kidney transplantation.

RESULTS

Of the 176 420 participants, 94 885 were women (53.8%); mean (SD) age was 42.5 (15.4) years. During a mean (SD) follow-up of 22.7 (6.9) years, 454 (0.3%) participants developed ESKD and 35 234 (20.0%) died. In multivariable-adjusted Cox proportional hazards models, the TyG index was significantly associated with the risk of ESKD, both with (hazard ratio [HR] per 1-SD increase, 1.68; 95% CI, 1.56-1.82) and without (HR per 1-SD increase, 1.79; 95% CI, 1.66-1.93) the inclusion of BMI as a covariate. Mediation analysis using a newly proposed 2-stage regression method for survival data showed that a 5-point increase in BMI increased the risk of ESKD by 58% (HR [total association], 1.58; 95% CI, 1.43-1.75), and that 41.7% of the total association (95% CI, 31.6%-51.8%) was mediated through the TyG index (HR [indirect association], 1.21; 95% CI, 1.18-1.25).

CONCLUSIONS AND RELEVANCE

This study found that the TyG index appeared to be associated with ESKD risk and mediates nearly half of the total association between BMI and ESKD in the general population. Public health efforts aiming at the reduction of body weight might decrease the kidney sequelae of insulin resistance and the burden of ESKD.

Microalbuminuria as a potential biomarker for Parkinson's disease severity: A hypothesis

Parkinson's disease (PD) is the second most common neurodegenerative condition characterized by motor and non-motor symptoms causing a great burden in patients' quality of life. PD has been associated with various metabolic factors such as diabetes, hypertension, and more recently chronic kidney disease where proteinuria has been associated with an increased risk. The presence of small amounts of albumin in urine, microalbuminuria, is a common biomarker for endothelial damage and a predictive factor for not only cardiovascular but also neurological dysfunction. Multiple studies have assessed potential biomarkers for PD progression with great heterogeneity, we hypothesize the use of microalbuminuria as a potential marker that correlates with PD severity and might represent a feasible and simple method of evaluating PD patients in clinical practice. Evidence supporting the present hypothesis comes from oxidative stress, insulin resistance, and endothelial dysfunction. Oxidative stress is a key element in PD pathogenesis; studies have shown lower antioxidant capacity as PD progresses. On the other side, insulin signaling plays an important role in neuronal growth and survival, with its resistance being associated with PD. Microalbuminuria has been associated with both processes; increased levels of oxidative stress markers and decreased insulin sensitivity, hence its screening in PD might reflect these common pathological mechanisms. Moreover, the low vitamin D levels observed in PD patients, which are correlated with endothelial dysfunction and disease severity, might contribute to microalbuminuria induction. More evidence on this vascular approach comes from white matter lesions (WML), observed in brain imaging, which have been significantly associated with motor and non-motor function in PD patients and are independently associated with microalbuminuria. In this manner, an oxidant and insulin resistant environment, along with low vitamin D levels in PD patients, which are associated with microalbuminuria, might contribute altogether to WML. As the latter are correlated with motor and non-motor function, microalbuminuria might thus give insight on PD status. Prospective cohort studies with an adequate sample size, follow-up, and a thorough battery of clinical tests for PD are needed to confirm this hypothesis.

Association of microalbuminuria with metabolic syndrome: a cross-sectional study in Bangladesh

BACKGROUND AND AIMS

The objectives of this study were to estimate the prevalence of microalbuminuria and examine the association of microalbuminuria with metabolic syndrome (MetS) and its component in a Bangladeshi adult cohort.

METHODS

This cross-sectional study included 175 subjects (84 males and 91 females; aged 19-59 years), recruited from the outdoor Department of Medicine and Endocrinology of a medical college hospital in Dhaka, Bangladesh. Lipid profile and fasting blood glucose (FBG) were measured in serum and albumin and creatinine were determined in urine samples. Microalbuminuria was defined as the urinary albumin-to-creatinine ratio (ACR) of 30 to 300 mg/g. The MetS was defined according to the criteria of the National Cholesterol Education Program (NECP). The association of microalbuminuria with MetS and its components was evaluated by multivariate logistic regression analysis.

RESULTS

Among the study subjects, 66.3% were hypertensive and 70.3% were diabetic individuals. Overall, the prevalence of microalbuminuria was 29.7% with 31% in males and 28.6% in females. Microalbuminuria was 2.6 fold higher in hypertensive and diabetic adults than in the non-hypertensive or non-diabetic adults. The prevalence of microalbuminuria was much more frequent in persons with the MetS (36.0%) than the persons without the MetS (5.4%). The levels of FBG, systolic blood pressure (SBP), diastolic blood pressure (DBP) and triglycerides were significantly higher (p < 0.01 for all cases) in subjects with microalbuminuria. In regression analysis, after adjusting for sex, age, and body mass index, microalbuminuria was strongly correlated with MetS followed by elevated BP and FBG (p < 0.01 for all cases).

CONCLUSIONS

Microalbuminuria was strongly associated with MetS in Bangladeshi adults. Elevated BP and FBG were the most predominant components of MetS among the study subjects. Comprehensive management of MetS at its early stage can be effective to prevent and reduce the progression of kidney injury and cardiovascular complications.

Insulin: Trigger and Target of Renal Functions

Kidney function in metabolism is often underestimated. Although the word “clearance” is associated to “degradation”, at nephron level, proper balance between what is truly degraded and what is redirected to de novo utilization is crucial for the maintenance of electrolytic and acid–basic balance and energy conservation. Insulin is probably one of the best examples of how diverse and heterogeneous kidney response can be. Kidney has a primary role in the degradation of insulin released in the bloodstream, but it is also incredibly susceptible to insulin action throughout the nephron. Fluctuations in insulin levels during fast and fed state add another layer of complexity in the understanding of kidney fine-tuning. This review aims at revisiting renal insulin actions and clearance and to address the association of kidney dysmetabolism with hyperinsulinemia and insulin resistance, both highly prevalent phenomena in modern society.

PPARG Pro12Ala Polymorphism with CKD in Asians: A Meta-Analysis Combined with a Case-Control Study-A Key for Reaching Null Association

BACKGROUND

So far, numerous meta-analyses have been published regarding the correlation between peroxisome proliferator-activated receptor gamma (PPARG) proline 12 alanine (Pro12Ala) gene polymorphism and chronic kidney disease (CKD); however, the results appear to be contradictory. Hence, this study is formulated with the objective of using existing meta-analysis data together with our research population to study the correlation between PPARG Pro12Ala gene polymorphism and CKD and evaluate whether an accurate result can be obtained.

METHODS

First, literature related to CKD and PPARG Pro12Ala available on the PubMed and EMBASE databases up to December 2016 was gathered from 20 publications. Then, the gathered results were combined with our case-control study of 1693 enrolled subjects and a trial sequential analysis (TSA) was performed to verify existing evidence and determine whether a firm conclusion can be drawn.

RESULTS

The TSA results showed that the cumulative sample size for the Asian sample was 6078 and was sufficient to support a definite result. The results of this study confirmed that there is no obvious correlation between PPARG Pro12Ala and CKD for Asians (OR = 0.82 (95% CI = 0.66-1.02), I² = 63.1%), but this was not confirmed for Caucasians. Furthermore, the case-control sample in our study was shown to be the key for reaching this conclusion.

CONCLUSIONS

The meta-analysis results of this study suggest no significant correlation between PPARG Pro12Ala gene polymorphism and CKD for Asians after adding our samples, but not for Caucasian.

A Mendelian Randomization Study Provides Evidence That Adiposity and Dyslipidemia Lead to Lower Urinary Albumin-to-Creatinine Ratio, a Marker of Microvascular Function

Urinary albumin-to-creatinine ratio (ACR) is a marker of diabetic nephropathy and microvascular damage. Metabolic-related traits are observationally associated with ACR, but their causal role is uncertain. Here, we confirmed ACR as a marker of microvascular damage and tested whether metabolic-related traits have causal relationships with ACR. The association between ACR and microvascular function (responses to acetylcholine [ACH] and sodium nitroprusside) was tested in the SUMMIT study. Two-sample Mendelian randomization (MR) was used to infer the causal effects of 11 metabolic risk factors, including glycemic, lipid, and adiposity traits, on ACR. MR was performed in up to 440,000 UK Biobank and 54,451 CKDGen participants. ACR was robustly associated with microvascular function measures in SUMMIT. Using MR, we inferred that higher triglyceride (TG) and LDL cholesterol (LDL-C) levels caused elevated ACR. A 1 SD higher TG and LDL-C level caused a 0.062 (95% CI 0.040, 0.083) and a 0.026 (95% CI 0.008, 0.044) SD higher ACR, respectively. There was evidence that higher body fat and visceral body fat distribution caused elevated ACR, while a metabolically "favorable adiposity" phenotype lowered ACR. ACR is a valid marker for microvascular function. MR suggested that seven traits have causal effects on ACR, highlighting the role of adiposity-related traits in causing lower microvascular function.

Insulin resistance is associated with urinary albumin-creatinine ratio in normal weight individuals with hypertension and diabetes: The REACTION study

BACKGROUND

The relationship between albuminuria and insulin resistance (IR) has not been clarified in previous studies. This study was conducted to examine whether IR is associated with albuminuria in subjects with diverse blood pressure and glycometabolism statuses.

METHODS

This study included 34 136 participants whose data were drawn from a cross-sectional survey named the 2011 REACTION study. The participants were divided into six groups. The urinary albumin-creatinine ratio (UACR) and glomerular filtration rate (GFR) were used as markers of chronic kidney disease (CKD). Variance tests and logistic regression models were performed for homeostatic model assessment of insulin resistance (HOMA-IR) in relation to UACR and eGFR.

RESULTS

First, UACR levels and HOMA-IR exhibited a positive correlation among participants (P < 0.05), and a negative correlation existed between GFR and HOMA-IR (P < 0.05). Second, in the hypertension with diabetes group, in individuals whose body mass index (BMI) was 18.5-24.0 kg/m² , age was 50-60 years old, low density lipoprotein cholesterol (LDL-C) was 2.6-3.4 mmol/L or high density lipoprotein cholesterol (HDL-C) was 0.9-1.55 mmol/L, HOMA-IR was positively associated with UACR (P < 0.05). However, there was a negative correlation between GFR and HOMA-IR in the hypertension with diabetes group in individuals whose BMI was 18.5-24.0 kg/m² or whose age was over 65 years old (P < 0.05).

CONCLUSIONS

In the context of different blood pressure and glycometabolism statuses, the positive correlation between UACR levels and HOMA-IR was affected by BMI, age, LDL-C, HDL-C, and GFR. In patients with hypertension and diabetes, the early detection and intervention of IR and related risk factors in patients with normal BMI may reduce the occurrence of microalbuminuria and delay the progression of CKD.

Effects of low skeletal muscle mass and sarcopenic obesity on albuminuria: a 7-year longitudinal study

We aimed to identify the association between low skeletal muscle, sarcopenic obesity, and the incidence of albuminuria in the general population using a longitudinal study. Data from 29,942 subjects who underwent two or more routine health examinations from 2006 to 2013 were retrospectively reviewed. Relative skeletal muscle mass was presented using the skeletal muscle mass index (SMI), a measure of body weight-adjusted appendicular skeletal muscle mass estimated by bioelectrical impedance analysis. The cumulative incidence of albuminuria was 981 (3.3%) during the 7-year follow-up period. The hazard ratio of incident albuminuria was 1.44 (95% CI: 1.22–1.71, p for trend <0.001) in the lowest SMI tertile relative to the highest SMI tertile after multivariable adjustment. After additionally adjusting for general and central obesity, the hazard ratio was 1.35 (95% CI: 1.13–1.61, p for trend = 0.001) and 1.30 (95% CI: 1.08–1.56, p for trend = 0.003), respectively. Furthermore, the risk of developing albuminuria was much higher in the sarcopenic obesity group (HR: 1.49, 95% CI: 1.21–1.81, p for trend <0.001) compared to the other groups. Sarcopenic obesity, as well as low skeletal muscle, may lead to albuminuria in general populations.

Impaired glucose tolerance and albuminuria in patients with chronic heart failure: a subanalysis of the SUPPORT trial

AIMS

The study aims to evaluate the prognostic significance of impaired glucose tolerance (IGT) with reference to albuminuria in patients with chronic heart failure (CHF).

METHODS AND RESULTS

We examined 535 CHF patients (mean 66 years, women 25%) in the control arm of our SUPPORT trial, in which we examined additive impact of olmesartan in hypertensive patients with symptomatic CHF treated with β-blockers and/or angiotensin-converting enzyme inhibitors. We examined the association between glycaemic abnormality (assessed by 75 g of oral glucose tolerance test) and albuminuria for a composite outcome of all-cause death, myocardial infarction, stroke, and HF hospitalization. IGT patients (N = 113, mean 67.2 years) were older and more frequently treated with β-blockers compared with those with normal glucose regulation (N = 142, mean 64.0 years) and those with diabetes mellitus (N = 280, mean 65.7 years). Multivariable Cox proportional hazard models revealed that, as compared with normal glucose regulation (NGR), IGT was associated with increased risk of the outcome when complicated by albuminuria [hazard ratio (HR) 2.25; 95% confidence interval (CI) 1.14-4.42; P = 0.019] but not when uncomplicated by albuminuria (HR 0.76; 95% CI 0.35-1.60, P = 0.47) (P for interaction = 0.041). This was also the case for diabetes mellitus and albuminuria (HR 2.06; 95% CI 1.17-3.61; P = 0.012). Among IGT patients without albuminuria, 21 (29%) developed albuminuria at 1-year visit, which was again associated with poor prognosis (HR 7.36; 95% CI 1.39-38.98, P = 0.019).

CONCLUSIONS

These results indicate that IGT is associated with poor prognosis when complicated by albuminuria in CHF patients, demonstrating the importance of combined early stages of glucose intolerance and renal dysfunction in the management of CHF.

Glycogen synthase kinase 3β hyperactivity in urinary exfoliated cells predicts progression of diabetic kidney disease

Burgeoning evidence points to glycogen synthase kinase (GSK)3β as a key player in diverse kidney diseases. However, as a pivotal transducer of the insulin signaling pathway, the role of GSK3β in diabetic kidney disease remains uncertain. In db/db mice, renal expression of total and activated GSK3β was increasingly elevated. This preceded the development of diabetic kidney disease, and correlated with the progression of signs of diabetic kidney injury, including albuminuria and extracellular matrix accumulation in glomeruli and tubulointerstitia. In vitro, exposure of glomerular podocytes, mesangial cells, and renal tubular cells to a diabetic milieu induced GSK3β overexpression and hyperactivity, which seem essential and sufficient for eliciting diabetic cellular damages in kidney cells, because the cytopathic effect of the diabetic milieu was mitigated by GSK3β knockdown, but was mimicked by ectopic expression of constitutively active GSK3β even in the normal milieu. In consistency, kidney biopsy specimens procured from patients with varying stages of diabetic nephropathy revealed an amplified expression of total and activated GSK3β in glomeruli and renal tubules, associated with the severity of diabetic nephropathy. Moreover, in retrospective cohorts of type 2 diabetic patients that were followed for over five years, the relative activity of GSK3β in banked urinary exfoliated cells represented an independent risk factor for development or progression of renal impairment. Furthermore, receiver operating characteristic curve analysis demonstrated that GSK3β activity in urinary exfoliated cells provided much better power than albuminuria in discriminating diabetic patients with progressive renal impairment from those with stable kidney function. Thus, renal expression and activity of GSK3β are amplified in experimental and clinical diabetic nephropathy. Hence, GSK3β in urinary exfoliated cells may serve as a novel biomarker for predicting diabetic kidney disease progression.

Molecular form and concentration of serum α2-macroglobulin in diabetes

α₂-Macroglobulin is a highly abundant serum protein involved in the development of atherosclerosis and cardiac hypertrophy. However, its circulating molecular form and exact concentrations in human health/diseases are not known. Blue native-polyacrylamide gel electrophoresis of human serum was used to confirm the native conformation of α₂-macroglobulin. We created an enzyme-linked immunosorbent assay suitable for quantifying its circulating molecular form and undertook a cross-sectional study to measure its serum levels in 248 patients with diabetes mellitus and 59 healthy volunteers. The predominant circulating molecular form of α₂-macroglobulin was the tetramer, whereas its dimer was detectable in patients with high serum levels of α₂-macroglobulin. The serum α₂-macroglobulin concentration was not associated with glycated hemoglobin or any other glycemic variable as evaluated from 48-h continuous glucose monitoring, but showed close correlation with left ventricular posterior wall thickness, carotid artery intima-media thickness, urinary albumin:creatinine ratio (ACR) and brachial–ankle pulse wave velocity (baPWV). Multivariate analysis revealed only the ACR and baPWV to be independent variables influencing serum levels of α₂-macroglobulin. Thus, an increased ACR and baPWV are associated with higher serum concentrations of α₂-macroglobulin, and the latter may contribute to the mechanism by which albuminuria increases the risk of developing cardiovascular diseases.

Effects of metreleptin on proteinuria in patients with lipodystrophy

CONTEXT

Patients with lipodystrophy have high prevalence of proteinuria.

OBJECTIVE

To assess kidney disease in patients with generalized (GLD) versus partial lipodystrophy (PLD), and effects metreleptin on proteinuria in patients with lipodystrophy.

DESIGN/SETTING/PATIENTS/INTERVENTION

Prospective, open-label studies of metreleptin treatment in patients with GLD and PLD at the National Institutes of Health, Bethesda, MD.

OUTCOME MEASURES

24-hour urinary albumin and protein excretion rates, estimated glomerular filtration rate (eGFR), and creatinine clearance (CrCl) were measured at baseline and during up to 24 months of metreleptin treatment. Patients with increases in medications affecting outcome measures were excluded.

RESULTS

At baseline, patients with GLD had significantly greater albuminuria, proteinuria, eGFR, and CrCl compared to patients with PLD. CrCl was above the normal range in 69% of patients with GLD, and 39% with PLD (P=0.02). With up to 24 months of metreleptin treatment, there were significant reductions in albuminuria and proteinuria in patients with GLD, but not in those with PLD. No changes in eGFR or CrCl were observed in patients with GLD or PLD during metreleptin treatment.

CONCLUSIONS

Patients with GLD had significantly greater proteinuria than those with PLD, which improved with metreleptin treatment. The mechanisms leading to proteinuria in lipodystrophy and improvements in proteinuria with metreleptin are not clear. Hyperfiltration was also more common in GLD versus PLD but did not change with metreleptin.

Probing insulin sensitivity in diabetic kidney disease: is there a stronger role for functional imaging?

Clinical and experimental evidence support a cause-effect relationship between altered insulin signaling and development of kidney disease of metabolic and non-metabolic origin. However, the current criteria to measure and/or estimate the insulin resistance (IR) are available as research tool but are very difficult to implement in the clinical practice. Therefore, a better understanding of the key players contributing to IR may lead to the development of new non-invasive tools to assess organ-specific insulin sensitivity (IS). We will therefore first introduce the concept that IR and kidney disease may be causally linked as suggested by clinical and experimental studies. We will then, expand on the potential mechanisms leading to altered renal insulin signaling. After reviewing the limitation of currently available strategies to determine IR, this review article will focus on imaging techniques that could be utilized to determine renal IR and that could be tested to predict kidney disease development and progression.

Dietary Flavonoids in the Prevention of T2D: An Overview

Type 2 diabetes (T2D) is a progressive metabolic disease that is increasing in prevalence globally. It is well established that insulin resistance (IR) and a progressive decline in functional β-cell mass are hallmarks of developing T2D. Obesity is a leading pathogenic factor for developing IR. Constant IR will progress to T2D when β-cells are unable to secret adequate amounts of insulin to compensate for decreased insulin sensitivity. Recently, a considerable amount of research has been devoted to identifying naturally occurring anti-diabetic compounds that are abundant in certain types of foods. Flavonoids are a group of polyphenols that have drawn great interest for their various health benefits. Results from many clinical and animal studies demonstrate that dietary intake of flavonoids might be helpful in preventing T2D, although cellular and molecular mechanisms underlying these effects are still not completely understood. This review discusses our current understanding of the pathophysiology of T2D and highlights the potential anti-diabetic effects of flavonoids and mechanisms of their actions.

Glucose Transporters in Diabetic Kidney Disease-Friends or Foes?

Diabetic kidney disease (DKD) is a major microvascular complication of diabetes and a common cause of end-stage renal disease worldwide. DKD manifests as an increased urinary protein excretion (albuminuria). Multiple studies have shown that insulin resistance correlates with the development of albuminuria in non-diabetic and diabetic patients. There is also accumulating evidence that glomerular epithelial cells or podocytes are insulin sensitive and that insulin signaling in podocytes is essential for maintaining normal kidney function. At the cellular level, the mechanisms leading to the development of insulin resistance include mutations in the insulin receptor gene, impairments in the phosphoinositide 3-kinase (PI3K)/AKT signaling pathway, or perturbations in the trafficking of glucose transporters (GLUTs), which mediate the uptake of glucose into cells. Podocytes express several GLUTs, including GLUT1, GLUT2, GLUT3, GLUT4, and GLUT8. Of these, the most studied ones are GLUT1 and GLUT4, both shown to be insulin responsive in podocytes. In the basal state, GLUT4 is preferentially located in perinuclear and cytosolic vesicular structures and to a lesser extent at the plasma membrane. After insulin stimulation, GLUT4 is sorted into GLUT4-containing vesicles (GCVs) that translocate to the plasma membrane. GCV trafficking consists of several steps, including approaching of the GCVs to the plasma membrane, tethering, and docking, after which the lipid bilayers of the GCVs and the plasma membrane fuse, delivering GLUT4 to the cell surface for glucose uptake into the cell. Studies have revealed novel molecular regulators of the GLUT trafficking in podocytes and unraveled unexpected roles for GLUT1 and GLUT4 in the development of DKD, summarized in this review. These findings pave the way for better understanding of the mechanistic pathways associated with the development and progression of DKD and aid in the development of new treatments for this devastating disease.

Insulin Resistance in Kidney Disease: Is There a Distinct Role Separate from That of Diabetes or Obesity?

Insulin resistance is a central component of the metabolic dysregulation observed in obesity, which puts one at risk for the development of type 2 diabetes and complications related to diabetes such as chronic kidney disease. Insulin resistance and compensatory hyperinsulinemia place one at risk for other risk factors such as dyslipidemia, hypertension, and proteinuria, e.g., development of kidney disease. Our traditional view of insulin actions focuses on insulin-sensitive tissues such as skeletal muscle, liver, adipose tissue, and the pancreas. However, insulin also has distinct actions in kidney tissue that regulate growth, hypertrophy, as well as microcirculatory and fibrotic pathways which, in turn, impact glomerular filtration, including that governed by tubuloglomerular feedback. However, it is often difficult to discern the distinct effects of excess circulating insulin and impaired insulin actions, as exist in the insulin resistance individual, from the associated effects of obesity or elevated systolic blood pressure on the development and progression of kidney disease over time. Therefore, we review the experimental and clinical evidence for the distinct impact of insulin resistance on kidney function and disease.

Microalbuminuria as a simple predictor of incident diabetes over 8 years in the Korean Genome and Epidemiology Study (KoGES)

Microalbuminuria (MAU) is a common subclinical disease and related with cardiovascular outcome both in diabetic and non-diabetic patients. However, there is rare data about the effect of MAU on the development of diabetes. Thus, we aimed to investigate whether MAU is associated with the development of incident diabetes. A total of 3385 subjects without diabetes (1503 men and 1882 women; mean age, 53 years) who participated in the Ansung–Ansan cohort study from 2001–2002 (baseline) to 2011–2012 (fifth follow-up visit) were followed for a mean of 8 years. The prevalence of MAU at baseline was 10.8% (365 patients), and the incidence of newly developed diabetes during the follow-up period was 15.3% (56 patients) in subjects with MAU. The hazard ratio (HR) for development of diabetes was 1.43 (95% confidence interval (CI) 1.07–1.91, p-value 0.016), independent of traditional risk factors for diabetes including pre-diabetes, age, obesity, and family history. The impact of MAU on diabetes was also significant in the non-pre-diabetic population (HR 2.08, 95% CI 1.07–4.03, p-value 0.031). In conclusion, our results show that incident MAU is associated with future development of diabetes and could be an early marker for diabetes, even in the non-prediabetic population.

Deficient Insulin-mediated Upregulation of the Equilibrative Nucleoside Transporter 2 Contributes to Chronically Increased Adenosine in Diabetic Glomerulopathy

Deficient insulin signaling is a key event mediating diabetic glomerulopathy. Additionally, diabetic kidney disease has been related to increased levels of adenosine. Therefore, we tested a link between insulin deficiency and dysregulated activity of the equilibrative nucleoside transporters (ENTs) responsible for controlling extracellular levels of adenosine. In ex vivo glomeruli, high D-glucose decreased nucleoside uptake mediated by ENT1 and ENT2 transporters, resulting in augmented extracellular levels of adenosine. This condition was reversed by exposure to insulin. Particularly, insulin through insulin receptor/PI3K pathway markedly upregulated ENT2 uptake activity to restores the extracellular basal level of adenosine. Using primary cultured rat podocytes as a cellular model, we found insulin was able to increase ENT2 maximal velocity of transport. Also, PI3K activity was necessary to maintain ENT2 protein levels in the long term. In glomeruli of streptozotocin-induced diabetic rats, insulin deficiency leads to decreased activity of ENT2 and chronically increased extracellular levels of adenosine. Treatment of diabetic rats with adenosine deaminase attenuated both the glomerular loss of nephrin and proteinuria. In conclusion, we evidenced ENT2 as a target of insulin signaling and sensitive to dysregulation in diabetes, leading to chronically increased extracellular adenosine levels and thereby setting conditions conducive to kidney injury.

Soluble urokinase receptor (suPAR) predicts microalbuminuria in patients at risk for type 2 diabetes mellitus

Early identification of patients at risk of developing diabetic nephropathy is essential. Elevated serum concentrations of soluble urokinase receptor (suPAR) associate with diabetes mellitus and predict onset and loss of renal function in chronic kidney disease. We hypothesize, that suPAR may be an early risk indicator for diabetic nephropathy, preceding microalbuminuria. The relationship of baseline suPAR and incident microalbuminuria was assessed in a prospective long-term cohort of subjects at increased risk for type 2 diabetes (TULIP, n = 258). Association with albuminuria at later stages of disease was studied in a cross-sectional cohort with manifest type 2 diabetes (ICEPHA, n = 266). A higher baseline suPAR was associated with an increased risk of new-onset microalbuminuria in subjects at risk for type 2 diabetes (hazard ratio 5.3 (95% CI 1.1-25.2, p = 0.03) for the highest vs. lowest suPAR quartile). The proportion of subjects with prediabetes at the end of observation was higher in subjects with new-onset microalbuminuria. suPAR consistently correlated with albuminuria in a separate cohort with manifest type 2 diabetes. Elevated baseline suPAR concentrations independently associate with new-onset microalbuminuria in subjects at increased risk of developing type 2 diabetes. suPAR may hence allow for earlier risk stratification than microalbuminuria.

DBA2J db/db mice are susceptible to early albuminuria and glomerulosclerosis that correlate with systemic insulin resistance

Diabetic nephropathy (DN) is the leading cause of kidney failure in the world. To understand important mechanisms underlying this condition, and to develop new therapies, good animal models are required. In mouse models of type 1 diabetes, the DBA/2J strain has been shown to be more susceptible to develop kidney disease than other common strains. We hypothesized this would also be the case in type 2 diabetes. We studied db/db and wild-type (wt) DBA/2J mice and compared these with the db/db BLKS/J mouse, which is currently the most widely used type 2 DN model. Mice were analyzed from age 6 to 12 wk for systemic insulin resistance, albuminuria, and glomerular histopathological and ultrastructural changes. Body weight and nonfasted blood glucose were increased by 8 wk in both genders, while systemic insulin resistance commenced by 6 wk in female and 8 wk in male db/db DBA/2J mice. The urinary albumin-to-creatinine ratio (ACR) was closely linked to systemic insulin resistance in both sexes and was increased ~50-fold by 12 wk of age in the db/db DBA/2J cohort. Glomerulosclerosis, foot process effacement, and glomerular basement membrane thickening were observed at 12 wk of age in db/db DBA/2J mice. Compared with db/db BLKS/J mice, db/db DBA/2J mice had significantly increased levels of urinary ACR, but similar glomerular histopathological and ultrastructural changes. The db/db DBA/2J mouse is a robust model of early-stage albuminuric DN, and its levels of albuminuria correlate closely with systemic insulin resistance. This mouse model will be helpful in defining early mechanisms of DN and ultimately the development of novel therapies.

Sarcopenia is associated with albuminuria independently of hypertension and diabetes: KNHANES 2008-2011

INTRODUCTION

Although sarcopenia is associated with metabolic disorders, its influence on albuminuria has not been determined. The aim of this study was to identify the relationship between sarcopenia and albuminuria in the general population.

METHODS

This was a population-based, cross-sectional study using a nationally representative sample of 2326 subjects aged ≥20years from the Korea National Health and Nutrition Examination Surveys of 2008-2011. Appendicular skeletal muscle (ASM) measured by dual-energy X-ray absorptiometry was used to assess sarcopenia, which was defined as ASM divided by body mass index, as recommended by the international consensus meeting of the National Institutes of Health. Albuminuria was defined as an albumin-to-creatinine ratio of ≥30mg/g using random spot urine samples.

RESULTS

A total of 385 (16.5%) subjects were classified as having albuminuria. Sarcopenic subjects showed a higher proportion of albuminuria than subjects without sarcopenia (odds ratios [ORs]=2.17-3.26, all P<0.05) after stratification based on the presence of hypertension, diabetes, or metabolic syndrome and a higher homeostasis model assessment of insulin resistance (all P<0.001). The albuminuria risk was comparable between insulin-sensitive subjects with sarcopenia and insulin-resistant subjects with preserved muscle mass. A multiple logistic regression analysis also demonstrated that sarcopenia was independently associated with albuminuria (OR=1.61, 95% confidence interval [CI]=1.04-2.48, P<0.05). The association between sarcopenia and albuminuria remained strong in the elderly population (ORs=1.80-2.68, P<0.05), whereas it lost its significance in the younger age group. Furthermore, the risk of albuminuria was much higher in sarcopenic obese subjects than in other groups (OR=4.90, 95% CI=3.23-7.43, P<0.001).

CONCLUSIONS

Sarcopenia was associated with an increased risk of albuminuria independent of hypertension, diabetes, and metabolic syndrome. Sarcopenia and obesity had a synergistic impact on the increased risk of albuminuria. This suggests that sarcopenic obesity as well as sarcopenia alone may be considered as novel risk factors for albuminuria.

Autophagy protects human podocytes from high glucose-induced injury by preventing insulin resistance

OBJECTIVE

Insulin resistance is correlated with the progress of albuminuria in diabetic patients, and podocytes are crucial for maintaining the normal function of the glomerular filtration barrier. In the present study, we aimed to investigate the high glucose-induced insulin resistance and cell injury in human podocytes and the putative role of autophagy in this process.

METHODS

Human podocytes were cultured in high glucose-supplemented medium and low glucose and high osmotic conditions were used for the controls. Autophagy in the podocytes was regulated using rapamycin or 3-methyladenine stimulation. Next, autophagy markers including LC3B, Beclin-1, and p62 were investigated using western blot and qPCR, and the insulin responsiveness was analyzed based on glucose uptake and by using the phosphorylation of the insulin receptor with Nephrin as a podocyte injury marker.

RESULTS

The basal autophagy level decreased under the high glucose conditions, which was accompanied by a decrease in the glucose uptake and phosphorylation of the insulin receptor in the human podocytes. More interestingly, the glucose uptake and the phosphorylation of the insulin receptor were decreased by 3-MA stimulation and increased by rapamycin, illustrating that the responsiveness of insulin was regulated by autophagy. The activation of autophagy by rapamycin also ameliorated cell injury in the human podocytes.

CONCLUSIONS

The presence or activation of autophagy was found to play a protective role in human podocytes against high glucose-induced insulin resistance and cell injury, which indicates a novel cellular mechanism and provides a potential therapeutic target for diabetic nephropathy (DN).

Glycated hemoglobin A1c level is associated with high urinary albumin/creatinine ratio in non-diabetic adult population

BACKGROUND

Regarding the association between glycated hemoglobin A1c (HbA1c) levels and microvascular complications, high HbA1c level in participants without diabetes mellitus (DM) may be associated with a high urinary albumin-to-creatinine ratio (UACR).

PATIENTS AND METHODS

Twelve thousand seven hundred and seventy four participants without DM were included in this study. The participants were divided into three groups according to HbA1c levels: a Low group (<5.7%), Middle group (5.7-6.0%), and High group (>6.0%). A high UACR was defined as UACR ≥3.9 mg/g for men and UACR ≥7.5 mg/g for women.

RESULTS

The proportions of participants with a high UACR in the Low, Middle, and High groups were 22.4%, 27.9%, and 38.1%, respectively. Both univariate and multivariate analyses showed that logUACR was greatest in the High group compared to the other groups. For participants without metabolic syndrome (MetS), the proportions of participants with high UACR and logUACR values were greatest in the High group compared to the other groups. For participants with MetS, no differences were found for proportions of participants with high UACR and logUACR values in the Low, Middle, and High groups.

CONCLUSION

Non-DM participants with relatively high HbA1c levels should be closely monitored for UACR, especially if participants do not have MetS. KEY MESSAGES HbA1c level was positively associated with the proportion of participants with a high UACR and logUACR in participants without DM. For participants without MetS, the proportion of participants with a high UACR was greater in the High group than in the other groups and logUACR was greatest in the High group compared to the other groups. For participants with MetS, there were significant associations between HbA1c and the proportion of participants with a high UACR as a categorical variable or logUACR as a continuous variable, but the statistical significance of this finding was weak. No differences were found for proportions of participants with high UACR and logUACR values in the Low, Middle, and High groups.

Review: Renin-angiotensin-aldosterone system intervention in the cardiometabolic syndrome and cardio-renal protection

The metabolic syndrome, also known as the cardiometabolic syndrome (CMS), is a state of metabolic and vascular dysregulation that is associated with activation of the renin-angiotensin-aldosterone system (RAAS). Clinical components of the CMS include central or visceral obesity, hypertension (HTN), dyslipidemia, insulin resistance/hyperinsulinemia, and microalbuminuria that collectively convey increases in oxidative stress, inflammation, and subsequent endothelial dysfunction. The cardio-renal inflammation and oxidative stress enhanced in the CMS increases the risk for cardiovascular disease (CVD) and renal disease end-points such as stroke, congestive heart failure, and chronic kidney disease (CKD). The development of proteinuria is known to herald progressive kidney disease (e.g. CKD) and both are now well accepted as CVD risk factors. Evidence suggests a role for visceral obesity, insulin resistance/hyperinsulinemia, HTN, and other components of the CMS lead to an increased risk for proteinuria and progressive loss of renal function. Intervention with agents that block the RAAS (e.g. ACE inhibitors and Angiotensin type 1 receptor blockers) have been shown to reduce proteinuria, CKD progression, and CVD events. Herein, we will examine the relationship between RAAS intervention and reductions in CKD and CVD events.

The dose-response effect of insulin sensitivity on albuminuria in children according to diabetes type

BACKGROUND

Insulin resistance is associated with microalbuminuria among youth with diabetes mellitus. We sought to determine the dose-response effect of insulin sensitivity (IS) on the magnitude of albuminuria and whether there is a threshold below which urine albumin excretion increases.

METHODS

These analyses included participants from the SEARCH for Diabetes in Youth Study with incident diabetes who completed a baseline study visit (n = 2988). We estimated IS using a validated equation incorporating waist circumference, HbA1C, and fasting serum triglycerides. Multivariate regression analyses were performed to assess the effect of IS on urine albumin creatinine ratio (UACR), stratified by diabetes type. The IS threshold was then determined using segmented regressions within each diabetes type and incorporated into the multivariate model.

RESULTS

There was an association between IS and UACR in type 2 diabetes only (beta = -0.39; p < 0.001). There was strong statistical evidence for a threshold effect of IS score on UACR in the group of youth with type 2 (beta = 0.40; p < 0.001) but not type 1 diabetes (p = 0.3).

CONCLUSIONS

In cross-sectional analyses, there is a negative association between IS and UACR in youth with type 2 but not type 1 diabetes, and this association likely includes a threshold effect of IS on UACR.

12-Lipoxygenase Inhibition on Microalbuminuria in Type-1 and Type-2 Diabetes Is Associated with Changes of Glomerular Angiotensin II Type 1 Receptor Related to Insulin Resistance

(1) BACKGROUND: 12-lipoxygenase (12-LO) is involved in the development of diabetic nephropathy (DN). In the present study, we investigated whether 12-LO inhibition may ameliorate type-2 DN (T2DN) by interfering with insulin resistance (IR); (2) METHODS: Rat glomerular mesangial cells, glomeruli and skeletal muscles were isolated and used in this study. Kidney histological changes were confirmed by periodic-acid Schiff staining; mRNA expression was detected by competitive reverse transcription polymerase chain reaction; and the protein level was determined by Western blot and the enzyme-linked immunosorbent assay, respectively; (3) RESULTS: The inhibition of 12-LO attenuated microalbuminuria (MAU) increases in type-2 diabetic rats, but not in type-1 diabetic rats. Infusion of 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE) significantly increased the expression of angiotensin II (Ang II) and Ang II type 1 receptor (AT1R), but decreased the expression of AT1R-associated protein (ATRAP) in rat glomeruli, compared to the control. An in vitro study revealed that both 12(S)-HETE and insulin upregulated AT1R expression in rat mesangial cells. In the presence of p38 mitogen-activated protein kinase (MAPK) inhibitor, SB202190, the 12(S)-HETE-induced ATRAP reduction was significantly abolished. Interestingly, 12-LO inhibition did not influence AT1R expression in type-1 diabetic rats, but significantly abolished the increased AT1R and Ang II expression in glomeruli of type-2 diabetic rats. Furthermore, the inhibition of 12-LO significantly corrected impaired insulin sensitivity and fast serum insulin level, as well as the p-AMP-activated protein kinase (AMPK) reduction in skeletal muscle of type-2 diabetic rats; (4) CONCLUSION: The inhibition of 12-LO potentially ameliorated MAU by preventing IR through the downregulation of glomerular AT1R expression in T2DN.