6,603 research outputs found
Role of anatomical location, cellular phenotype and perfusion of adipose tissue in intermediary metabolism: A narrative review
No full textIt is well-established that adipose tissue accumulation is associated with insulin resistance through multiple mechanisms. One major metabolic link is the classical Randle cycle: enhanced release of free fatty acids (FFA) from hydrolysis of adipose tissue triglycerides impedes insulin-mediated glucose uptake in muscle tissues. Less well studied are the different routes of this communication. First, white adipose tissue depots may be regionally distant from muscle (i.e., gluteal fat and diaphragm muscle) or contiguous to muscle but separated by a fascia (Scarpa’s fascia in the abdomen, fascia lata in the thigh). In this case, released FFA outflow through the venous drainage and merge into arterial plasma to be transported to muscle tissues. Next, cytosolic triglycerides can directly, i.e., within the cell, provide FFA to myocytes (but also pancreatic ß-cells, renal tubular cells, etc.). Finally, adipocyte layers or lumps may be adjacent to, but not anatomically segregated, from muscle, as is typically the case for epicardial fat and cardiomyocytes. As regulation of these three main delivery paths is different, their separate contribution to substrate competition at the whole-body level is uncertain. Another important link between fat and muscle is vascular. In the resting state, blood flow is generally higher in adipose tissue than in muscle. In the insulinized state, fat blood flow is directly related to whole-body insulin resistance whereas muscle blood flow is not; consequently, fractional (i.e., flow-adjusted) glucose uptake is stimulated in muscle but not fat. Thus, reduced blood supply is a major factor for the impairment of in vivo insulin-mediated glucose uptake in both subcutaneous and visceral fat. In contrast, the insulin resistance of glucose uptake in resting skeletal muscle is predominantly a cellular defect
Extremes of both weight gain and weight loss are associated with increased incidence of heart failure and cardiovascular death: evidence from the CANVAS Program and CREDENCE
No full textAbstract Background Obesity is an independent risk factor for cardiovascular disease (CVD) in patients with type 2 diabetes (T2D). However, it is not known to what extent weight fluctuations might be associated with adverse outcomes. We aimed at assessing the associations between extreme weight changes and cardiovascular outcomes in two large randomised controlled trials of canagliflozin in patients with T2D and high cardiovascular (CV) risk. Methods In the study populations of the CANVAS Program and CREDENCE trials, weight change was evaluated between randomization and week 52–78, defining subjects in the top 10% of the entire distribution of weight changes as gainers, subjects in the bottom 10% as losers and the remainder as stable. Univariate and multivariate Cox proportional hazards models were used to test the associations between weight changes categories, randomised treatment and covariates with heart failure hospitalisation (hHF) and the composite of hHF and CV death. Results Median weight gain was 4.5 kg in gainers and median weight loss was 8.5 kg in losers. The clinical phenotype of gainers as well as that of losers were similar to that of stable subjects. Weight change within each category was only slightly larger with canagliflozin than placebo. In both trials, gainers and losers had a higher risk of hHF and of hHF/CV death compared with stable at univariate analysis. In CANVAS, this association was still significant by multivariate analysis for hHF/CV death in both gainers and losers vs. stable (hazard ratio – HR 1.61 [95% confidence interval - CI: 1.20–2.16] and 1.53 [95% CI 1.14–2.03] respectively). Results were similar in CREDENCE for gainers vs. stable (adjusted HR for hHF/CV death 1.62 [95% CI 1.19–2.16]) Conclusions Extremes of weight gain or loss were independently associated with a higher risk of the composite of hHF and CV death. In patients with T2D and high CV risk, large changes in body weight should be carefully assessed in view of individualised management. Trials registration CANVAS ClinicalTrials.gov number: NCT01032629. CREDENCE ClinicalTrials.gov number: NCT0206579
The Stunned beta Cell: A Brief History
No full textbeta cell dysfunction is sufficient to cause hyperglycemia; beta cell loss is not necessary but, if severe, can be sufficient and may be accompanied by intrinsic beta cell dysfunction. Clinical testing can differentiate beta cell capacity from beta cell glucose sensitivity but cannot ascribe either to relative changes in beta cell mass versus function. However, longitudinal and intervention studies indicate that beta cell glucose insensitivity (stunning) closely tracks with hyperglycemia and is, at least in part, reversible. Rescuing stunned beta cells is a key therapeutic target
Insulin resistance and normal thyroid hormone levels: prospective study and metabolomic analysis
No full textWhile hyperthyroidism and hypothyroidism cause dysglycemia, the relationship between thyroid hormone levels within the normal range and insulin resistance (IR) is unclear. In 940 participants with strictly normal serum concentrations of free triiodothyronine (fT3), free thyroxine (fT4), and thyroid-stimulating hormone (TSH) followed up for 3 yr, we measured insulin sensitivity (by the insulin clamp technique) and 35 circulating metabolites. At baseline, across quartiles of increasing fT3 levels (or fT3/fT4 ratio) most features of IR emerged [i.e., male sex, greater body mass index (BMI), waist circumference, heart rate, blood pressure, fatty liver index, free fatty acids, and triglycerides; reduced insulin-mediated glucose disposal; and β-cell glucose sensitivity). In multiadjusted analyses, fT3 was reciprocally related to insulin sensitivity and, in a subset of 303 subjects, directly related to endogenous glucose production. In multiple regression models adjusting for sex, age, BMI, and baseline value of insulin sensitivity, higher baseline fT3 levels were significant predictors of decreases in insulin sensitivity. Moreover, baseline fT3 predicted follow-up increases in glycemia independently of sex, age, BMI, insulin sensitivity, β-cell glucose sensitivity, and baseline glycemia. Serum tyrosine levels were higher with IR and were directly associated with fT3; higher α-hydroxybutyrate levels signaled enhanced oxidative stress, thereby impairing tyrosine degradation. In 25 patients with morbid obesity, surgery-induced weight loss improved IR and consensually lowered fT3 levels. High-normal fT3 levels are associated with IR both cross-sectionally and longitudinally, and predict deterioration of glucose tolerance. This association is supported by a metabolite pattern that points at increased oxidative stress as part of the IR syndrome
Effect of empagliflozin on plasma proprotein convertase subtilisin/kexin type 9 (PCSK9) in patients with type 2 diabetes
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