Patricia C. Underwood

Preoperative A1C and clinical outcomes in patients with diabetes undergoing major noncardiac surgical procedures.

OBJECTIVE To evaluate the relationship between preoperative A1C and clinical outcomes in individuals with diabetes mellitus undergoing noncardiac surgery. RESEARCH DESIGN AND METHODS Data were obtained from the National Surgical Quality Improvement Program database and the Research Patient Data Registry of the Brigham and Women’s Hospital. Patients admitted to the hospital for ≥1 day after undergoing noncardiac surgery from 2005 to 2010 were included in the study. RESULTS Of 1,775 patients with diabetes, 622 patients (35%) had an A1C value available within 3 months before surgery. After excluding same-day surgeries, patients with diabetes were divided into four groups (A1C ≤6.5% [N = 109]; >6.5–8% [N = 202]; >8–10% [N = 91]; >10% [N = 47]) and compared with age-, sex-, and BMI-matched nondiabetic control subjects (N = 888). Individuals with A1C values between 6.5 and 8% had a hospital length of stay (LOS) similar to the matched control group (P = 0.5). However, in individuals with A1C values ≤6.5 or >8%, the hospital LOS was significantly longer compared with the control group (P < 0.05). Multivariate regression analysis demonstrated that a higher A1C value was associated with increased hospital LOS after adjustments for age, sex, BMI, race, type of surgery, Charlson Comordity Index, smoking status, and glucose level on the day of surgery (P = 0.02). There were too few events to meaningfully evaluate for death, infections, or readmission rate. CONCLUSIONS Our study suggests that chronic hyperglycemia (A1C >8%) is associated with poor surgical outcomes (longer hospital LOS). Providing a preoperative intervention to improve glycemic control in individuals with A1C values >8% may improve surgical outcomes, but prospective studies are needed.

Salt Sensitivity of Blood Pressure Is Associated With Polymorphisms in the Sodium-Bicarbonate Cotransporter

Previous studies have demonstrated that single nucleotide polymorphisms (SNPs) of the sodium-bicarbonate co-transporter gene (SLC4A5) are associated with hypertension. We tested the hypothesis that SNPs in SLC4A5 are associated with salt sensitivity of blood pressure in 185 whites consuming an isocaloric constant diet with a randomized order of 7 days of low Na+ (10 mmol/d) and 7 days of high Na+ (300 mmol/d) intake. Salt sensitivity was defined as a ≥7-mm Hg increase in mean arterial pressure during a randomized transition between high and low Na+ diet. A total of 35 polymorphisms in 17 candidate genes were assayed, 25 of which were tested for association. Association analyses with salt sensitivity revealed 3 variants that associated with salt sensitivity, 2 in SLC4A5 (P<0.001) and 1 in GRK4 (P=0.020). Of these, 2 SNPs in SLC4A5 (rs7571842 and rs10177833) demonstrated highly significant results and large effects sizes, using logistic regression. These 2 SNPs had P values of 1.0×10−4 and 3.1×10−4 with odds ratios of 0.221 and 0.221 in unadjusted regression models, respectively, with the G allele at both sites conferring protection. These SNPs remained significant after adjusting for body mass index and age (P=8.9×10−5 and 2.6×10−4 and odds ratios 0.210 and 0.286, respectively). Furthermore, the association of these SNPs with salt sensitivity was replicated in a second hypertensive population. Meta-analysis demonstrated significant associations of both SNPs with salt sensitivity (rs7571842 [P=1.2×10−5]; rs1017783 [P=1.1×10−4]). In conclusion, SLC4A5 variants are strongly associated with salt sensitivity of blood pressure in 2 separate white populations.

The Renin Angiotensin Aldosterone System and Insulin Resistance in Humans

Alterations in the renin angiotensin aldosterone system (RAAS) contribute to the underlying pathophysiology of insulin resistance in humans; however, individual differences in the treatment response of insulin resistance to RAAS blockade persist. Thus, understanding inter-individual differences in the relationship between the RAAS and insulin resistance may provide insights into improved personalized treatments and improved outcomes. The effects of the systemic RAAS on blood pressure regulation and glucose metabolism have been studied extensively; however, recent discoveries on the influence of local tissue RAAS in the skeletal muscle, heart, vasculature, adipocytes, and pancreas have led to an improved understanding of how activated tissue RAAS influences the development of insulin resistance and diabetes in humans. Angiotensin II (ANGII) is the predominant RAAS component contributing to insulin resistance; however, other players such as aldosterone, renin, and ACE2 are also involved. This review examines the role of local ANGII activity on insulin resistance development in skeletal muscle, adipocytes, and pancreas, followed by a discussion of the other RAAS components implicated in insulin resistance, including ACE2, Ang1-7, renin, and aldosterone.

The influence of body mass index and renin–angiotensin–aldosterone system activity on the relationship between 25-hydroxyvitamin D and adiponectin in Caucasian men

OBJECTIVE Previous studies have suggested that circulating adiponectin concentrations are associated positively with vitamin D and negatively with body mass index (BMI) but have not accounted for the influence of the renin-angiotensin-aldosterone system (RAAS) in this relationship. This is particularly relevant because increased RAAS activity is associated with obesity and is known to lower adiponectin levels. We evaluated the association between adiponectin and 25-hydroxyvitamin D (25(OH)D) after controlling RAAS activity with dietary sodium equilibration and also evaluated whether this relationship was influenced by BMI. DESIGN Cross-sectional study of 115 hypertensive Caucasian men from the Hypertensive Pathotype Consortium. METHODS To manipulate RAAS activity, all subjects underwent 1 week of high dietary sodium (HS) diet to suppress RAAS and 1 week of low dietary sodium (LS) diet to stimulate RAAS. Linear regression was used to evaluate the association between adiponectin and 25(OH)D, and the effect of BMI on this relationship, in each dietary condition. RESULTS Adiponectin was higher on HS, where circulating RAAS activity was low, when compared with LS (HS=2.9 versus LS=2.4 μg/ml, P<0.0001). 25(OH)D levels were positively associated with adiponectin, and BMI was a statistically significant effect modifier of the relationship between 25(OH)D and adiponectin on both diets (P interaction <0.01 between BMI and 25(OH)D). CONCLUSIONS Higher 25(OH)D concentrations were independently associated with higher adiponectin levels, particularly when BMI was high. Dietary sodium balance and circulating RAAS activity did not appear to affect this relationship. Future studies should explore whether vitamin D supplementation increases adiponectin levels in obesity.

Variants of the Caveolin-1 Gene: A Translational Investigation Linking Insulin Resistance and Hypertension

CONTEXT The co-occurrence of insulin resistance (IR) and hypertension is a heritable condition leading to cardiovascular complications. Caveolin-1 (CAV1), a gene previously associated with metabolic dysfunction in animal and cellular models, may be a marker for these conditions in humans. OBJECTIVE The objective of the study was to examine the relationship between CAV1 variants and IR in two hypertensive cohorts and to corroborate the findings in a CAV1 knockout mouse. DESIGN, SETTING, AND PARTICIPANTS A candidate gene association study was conducted in two hypertensive cohorts: 1) Caucasian and 2) Hispanic. Multivariate associations between individual variants and insulin-resistant phenotypes were analyzed, accounting for age, gender, body mass index, and sibling relatedness. Intraperitoneal glucose tolerance tests were conducted in wild-type and CAV1 knockout mice. RESULTS In the Caucasian hypertensive cohort, minor allele carriers of two CAV1 single-nucleotide polymorphisms (rs926198, rs3807989) had significantly higher fasting insulin levels (P = 0.005, P = 0.007), increased homeostatic assessment model for insulin resistance (HOMA-IR) (P =0.005, P = 0.008), and decreased M value during hyperinsulinemic, euglycemic clamp procedure (P = 0.004, P = 0.05) than major allele homozygotes. Findings were replicated in the Hispanic hypertensive cohort cohort for fasting insulin levels (P = 0.005, P = 0.02) and HOMA-IR (P = 0.008 and P = 0.02). Meta-analysis demonstrated significant associations of both single-nucleotide polymorphisms with fasting insulin levels (P = 0.00008, P = 0.0004) and HOMA-IR (P = 0.0001, P = 0.0004). As compared with wild type, CAV1 knockout mice displayed higher blood pressure levels and higher fasting glucose, insulin, and HOMA-IR levels and an exaggerated glycemic response to a glucose challenge. CONCLUSION Variations in the CAV1 gene are associated with IR and hypertension. CAV1 gene polymorphisms may be a biomarker for IR and hypertension, enabling earlier detection and improved treatment strategies.

Abnormal aldosterone physiology and cardiometabolic risk factors.

Abnormal aldosterone physiology has been implicated in the pathogenesis of cardiometabolic diseases. Single aldosterone measurements capture only a limited range of aldosterone physiology. New methods of characterizing aldosterone physiology may provide a more comprehensive understanding of its relationship with cardiometabolic disease. We evaluated whether novel indices of aldosterone responses to dietary sodium modulation, the sodium-modulated aldosterone suppression-stimulation index (SASSI for serum and SAUSSI for urine), could predict cardiometabolic risk factors. We performed cross-sectional analyses on 539 subjects studied on liberal and restricted sodium diets with serum and urinary aldosterone measurements. SASSI and SAUSSI were calculated as the ratio of aldosterone on liberal (maximally suppressed aldosterone) to the aldosterone on restricted (stimulated aldosterone) diets and associated with risk factors using adjusted regression models. Cardiometabolic risk factors associated with either impaired suppression of aldosterone on liberal diet, or impaired stimulation on restricted diet, or both; in all of these individual cases, these risk factors associated with higher SASSI or SAUSSI. In the context of abnormalities that constitute the metabolic syndrome, there was a strong positive association between the number of metabolic syndrome components (0–4) and both SASSI and SAUSSI (P<0.0001) that was independent of known aldosterone secretagogues (angiotensin II, corticotropin, potassium). SASSI and SAUSSI exhibited a high sensitivity in detecting normal individuals with zero metabolic syndrome components (86% for SASSI and 83% for SAUSSI). Assessing the physiological range of aldosterone responses may provide greater insights into adrenal pathophysiology. Dysregulated aldosterone physiology may contribute to, or result from, early cardiometabolic abnormalities.

Pharmacotherapy of type 2 diabetes: An update

Type 2 diabetes (T2DM) is a leading cause of morbidity and mortality worldwide and a major economic burden. The prevalence of T2DM is rising, suggesting more effective prevention and treatment strategies are necessary. The aim of this narrative review is to summarize the pharmacologic treatment options available for patients with T2DM. Each therapeutic class is presented in detail, outlining medication effects, side effects, glycemic control, effect on weight, indications and contraindications, and use in selected populations (heart failure, renal insufficiency, obesity and the elderly). We also present representative cost for each antidiabetic category. Then, we provide an individualized guide for initiation and intensification of treatment and discuss the considerations and rationale for an individualized glycemic goal.

Aldosterone Dysregulation With Aging Predicts Renal Vascular Function and Cardiovascular Risk

Aging and abnormal aldosterone regulation are both associated with vascular disease. We hypothesized that aldosterone dysregulation influences the age-related risk of renal vascular and cardiovascular disease. We conducted an analysis of 562 subjects who underwent detailed investigations under conditions of liberal and restricted dietary sodium intake (1124 visits) in the General Clinical Research Center. Aldosterone regulation was characterized by the ratio of maximal suppression to stimulation (supine serum aldosterone on a liberal sodium diet divided by the same measure on a restricted sodium diet). We previously demonstrated that higher levels of this Sodium-modulated Aldosterone Suppression-Stimulation Index (SASSI) indicate greater aldosterone dysregulation. Renal plasma flow (RPF) was determined via p-aminohippurate clearance to assess basal renal hemodynamics and the renal vascular responses to dietary sodium manipulation and angiotensin II infusion. Cardiovascular risk was calculated using the Framingham Risk Score. In univariate linear regression, older age (&bgr;=−4.60; P<0.0001) and higher SASSI (&bgr;=−58.63; P=0.001) predicted lower RPF and a blunted RPF response to sodium loading and angiotensin II infusion. We observed a continuous, independent, multivariate-adjusted interaction between age and SASSI, where the inverse relationship between SASSI and RPF was most apparent with older age (P<0.05). Higher SASSI and lower RPF independently predicted higher Framingham Risk Score (P<0.0001) and together displayed an additive effect. Aldosterone regulation and age may interact to mediate renal vascular disease. Our findings suggest that the combination of aldosterone dysregulation and renal vascular dysfunction could additively increase the risk of future cardiovascular outcomes; therefore, aldosterone dysregulation may represent a modifiable mechanism of age-related vascular disease.

Replication and Meta-analysis of the Gene-Environment Interaction between Body Mass Index and the Interleukin-6 Promoter Polymorphism with Higher Insulin Resistance

Insulin resistance (IR) is a complex disorder caused by an interplay of both genetic and environmental factors. Recent studies identified a significant interaction between body mass index (BMI) and the rs1800795 polymorphism of the interleukin-6 gene that influences both IR and onset of type 2 diabetes mellitus, with obese individuals homozygous for the C allele demonstrating the highest level of IR and greatest risk for type 2 diabetes mellitus. Replication of a gene-environment interaction is important to confirm the validity of the initial finding and extend the generalizability of the results to other populations. Thus, the objective of this study was to replicate this gene-environment interaction on IR in a hypertensive population and perform a meta-analysis with prior published results. The replication analysis was performed using white individuals with hypertension from the Hypertensive Pathotype cohort (N = 311), genotyped for rs1800795. Phenotype studies were conducted after participants consumed 2 diets--high sodium (200 mmol/d) and low sodium (10 mmol/d)--for 7 days each. Measurements for plasma glucose, insulin, and interleukin-6 were obtained after 8 hours of fasting. Insulin resistance was characterized by the homeostatic model assessment (HOMA-IR). In Hypertensive Pathotype, BMI was a significant effect modifier of the relationship between rs1800795 and HOMA-IR; higher BMI was associated with higher HOMA-IR among homozygote CC individuals when compared with major allele G carriers (P = .003). Furthermore, the meta-analysis in 1028 individuals confirmed the result, demonstrating the same significant interaction between rs1800795 and BMI on HOMA-IR (P = 1.05 × 10(-6)). This rare replication of a gene-environment interaction extends the generalizability of the results to hypertension while highlighting this polymorphism as a marker of IR in obese individuals.

The association of plasma resistin with dietary sodium manipulation, the renin‐angiotensin‐aldosterone system, and 25‐Hydroxyvitamin D3 in human hypertension

Objective  Both resistin and vitamin D have been associated with the renin‐angiotensin‐aldosterone system (RAAS). We investigated the association between resistin and the RAAS, and resistin and vitamin D under controlled dietary sodium conditions.