Kidney function, β-cell function and glucose tolerance in older men

Association of blood urea nitrogen to creatinine ratio with incident type 2 diabetes mellitus: A retrospective cohort study in the Chinese population

Renal dysfunction can lead to insulin resistance and increase the incidence of type 2 diabetes mellitus (T2DM). The blood urea nitrogen to creatinine ratio (NCR) is a frequently used indicator to assess renal dysfunction and differentiate between prerenal and intrinsic renal injury. However, the association between NCR and T2DM in the Chinese population remains unclear. Hence, this study aimed to investigate the association between NCR and the incidence of T2DM in the Chinese population. The relationship between NCR and T2DM was examined using the Cox proportional hazards model and curve fitting techniques. In addition, a comprehensive set of sensitivity and subgroup analyses were performed. All results were presented as hazard ratios (HRs) and 95% confidence intervals (CIs). Between 2010 and 2016, 189,416 Chinese people were recruited from the Rich Healthcare Group for this retrospective cohort study. Of the participants, 3755 (19.8%) were diagnosed with T2DM during the follow-up period. After full adjustment, the Cox proportional hazards model revealed a positive connection between NCR and the incidence of T2DM (HR = 1.03, 95% CI: 1.02-1.04, P < .001). Compared with individuals with lower NCR Q1 (≤13.536), the multivariate HR for NCR and T2DM in Q2 (13.536-16.256), Q3 (16.256-19.638), Q4 (>19.638) were 1.08 (0.98-1.19), 1.16 (1.05-1.28), 1.39 (1.26-1.53). The higher NCR groups (≥20) had a higher ratio of T2DM (HR = 1.28, 95% CI: 1.18-1.38, P < .001) than the lowest NCR group (<20). These findings were validated using sensitivity and subgroup analyses. In conclusion, this study found a positive and independent association between NCR and the incidence of T2DM after adjusting for confounding variables.

Human Beta Cell Functional Adaptation and Dysfunction in Insulin Resistance and Its Reversibility

BACKGROUND

Beta cells play a key role in the pathophysiology of diabetes since their functional adaptation is able to maintain euglycemia in the face of insulin resistance, and beta cell decompensation or dysfunction is a necessary condition for full-blown type 2 diabetes (T2D). The mechanisms behind compensation and decompensation are incompletely understood, especially for human beta cells, and even less is known about influences of chronic kidney disease (CKD) or immunosupressive therapy after transplantation on these processes and the development of posttransplant diabetes.

SUMMARY

During compensation, beta cell sensitivity to glucose becomes left-shifted, i.e., their sensitivity to stimulation increases, and this is accompanied by enhanced signals along the stimulus-secretion coupling cascade from membrane depolarization to intracellular calcium and the most distal insulin secretion dynamics. There is currently no clear evidence regarding changes in intercellular coupling during this stage of disease progression. During decompensation, intracellular stimulus-secretion coupling remains enhanced to some extent at low or basal glucose concentrations but seems to become unable to generate effective signals to stimulate insulin secretion at high or otherwise stimulatory glucose concentrations. Additionally, intercellular coupling becomes disrupted, lowering the number of cells that contribute to secretion. During progression of CKD, beta cells also seem to drift from a compensatory left-shift to failure, and immunosupressants can further impair beta cell function following kidney transplantation.

KEY MESSAGES

Beta cell stimulus-secretion coupling is enhanced in compensated insulin resistance. With worsening insulin resistance, both intra- and intercellular coupling become disrupted. CKD can progressively disrupt beta cell function, but further studies are needed, especially regarding changes in intercellular coupling.

Association and risk factors of chronic kidney disease and incident diabetes: a nationwide population-based cohort study

AIMS/HYPOTHESIS

Chronic kidney disease (CKD) is a known complication of diabetes mellitus, and insulin resistance is a well-known complication of CKD. However, there is no consensus in the published data on the association of CKD with incident diabetes.

METHODS

A total of 15,403 people with CKD were identified from the Taiwan National Health Insurance Research Database to determine their risk of incident diabetes compared with that of 15,403 matched individuals without CKD. Fine and Gray regression models using death as a competing risk were performed to calculate adjusted HRs and 95% CIs. Risk factors for incident diabetes in people with CKD were also determined.

RESULTS

The CKD cohort had a higher incidence rate of diabetes compared with the non-CKD cohort (11.23/1000 person-years vs 8.93/1000 person-years). In the fully adjusted model, CKD was a significant and independent predictor of incident diabetes (adjusted HR 1.204; 95% CI 1.11, 1.31). The influence of CKD on incident diabetes showed consistent results in three levels of sensitivity analysis. In the CKD cohort, the significant risk factors for incident diabetes included increased age, geographical location, hypertension, hyperlipidaemia and gout. Of these, hypertension was associated with the highest risk of developing incident diabetes (adjusted HR 1.682; 95% CI 1.47, 1.93).

CONCLUSIONS/INTERPRETATION

People with CKD were at higher risk of developing incident diabetes. People with CKD and hypertension, hyperlipidaemia, increased age or gout and who lived in certain geographical regions of Taiwan were more likely to develop diabetes as a complication compared with people without those characteristics.

Metabolic Abnormalities in Diabetes and Kidney Disease: Role of Uremic Toxins

PURPOSE OF REVIEW

Chronic kidney disease (CKD) is characterized by the accumulation of uremic retention solutes (URS) and is associated with perturbations of glucose homeostasis even in absence of diabetes. The underlying mechanisms of insulin resistance, β cell failure, and increase risk of diabetes in CKD, however, remain unclear. Metabolomic studies reported that some metabolites are similar in CKD and diabetic kidney disease (DKD) and contribute to the progression to end-stage renal disease. We attempted to discuss the mechanisms involved in the disruption of carbohydrate metabolism in CKD by focusing on the specific role of URS.

RECENT FINDINGS

Recent clinical data have demonstrated a defect of insulin secretion in CKD. Several studies highlighted the direct role of some URS (urea, trimethylamine N-oxide (TMAO), p-cresyl sulfate, 3-carboxylic acid 4-methyl-5-propyl-2-furan propionic (CMPF)) in glucose homeostasis abnormalities and diabetes incidence. Gut dysbiosis has been identified as a potential contributor to diabetes and to the production of URS. The complex interplay between the gut microbiota, kidney, pancreas β cell, and peripheral insulin target tissues has brought out new hypotheses for the pathogenesis of CKD and DKD. The characterization of intestinal microbiota and its associated metabolites are likely to fill fundamental knowledge gaps leading to innovative research, clinical trials, and new treatments for CKD and DKD.

Insulin resistance in chronic kidney disease

This review provides an overview of insulin resistance (IR) in patients with chronic kidney disease (CKD). IR is a pathological state in which target tissues fail to respond normally to insulin. IR is understood as a consequence of CKD and its prevalence rises particularly in advanced CKD stages. Mechanisms leading to IR are complex and multifactorial, involving post-receptor signaling defects, unhealthy lifestyles, metabolic acidosis, inflammation, oxidative stress, vitamin D deficiency, anemia, and uremic toxicity, as shown by human and experimental studies over the last 30 years. Whereas hyperinsulinemic euglycemic clamp is the gold standard, it is unpractical at the bedside, and either estimated IR indices by fasting glucose or insulin and oral glucose tolerance tests (OGTT) provide satisfactory estimates of IR also in patients with CKD. IR is likely to play a key role in the development of cardiometabolic complications, but not all studies associate IR with the risk of cardiovascular events and death. Various interventions at the level of lifestyle modifications, adaptations in dialysis therapy (such as use of icodextrin based solutions) and pharmacological strategies such as thiazolidinediones or vitamin D therapy may improve IR in patient with CKD.

Mechanism of insulin resistance in a rat model of kidney disease and the risk of developing type 2 diabetes

Chronic kidney disease is associated with homeostatic imbalances such as insulin resistance. However, the underlying mechanisms leading to these imbalances and whether they promote the development of type 2 diabetes is unknown. The effect of chronic kidney disease on insulin resistance was studied on two different rat strains. First, in a 5/6^th nephrectomised Sprague-Dawley rat model of chronic kidney disease, we observed a correlation between the severity of chronic kidney disease and hyperglycemia as evaluated by serum fructosamine levels (p<0.0001). Further, glucose tolerance tests indicated an increase of 25% in glycemia in chronic kidney disease rats (p<0.0001) as compared to controls whereas insulin levels remained unchanged. We also observed modulation of glucose transporters expression in several tissues such as the liver (decrease of ≈40%, p≤0.01) and muscles (decrease of ≈29%, p≤0.05). Despite a significant reduction of ≈37% in insulin-dependent glucose uptake in the muscles of chronic kidney disease rats (p<0.0001), the development of type 2 diabetes was never observed. Second, in a rat model of metabolic syndrome (Zucker Lepr^fa/fa), chronic kidney disease caused a 50% increased fasting hyperglycemia (p<0.0001) and an exacerbated glycemic response (p<0.0001) during glucose challenge. Similar modulations of glucose transporters expression and glucose uptake were observed in the two models. However, 30% (p<0.05) of chronic kidney disease Zucker rats developed characteristics of type 2 diabetes. Thus, our results suggest that downregulation of GLUT4 in skeletal muscle may be associated with insulin resistance in chronic kidney disease and could lead to type 2 diabetes in predisposed animals.