Relationship between simple markers of insulin resistance and coronary artery calcification

Association between hemoglobin A1c and abdominal aortic calcification: results from the National Health and Nutrition Examination Survey 2013-2014

BACKGROUND

Hemoglobin A1c (HbA1c), a "gold standard" for the assessment of glycemic control, was associated with an increased risk of cardiovascular disease and coronary artery calcification. However, its effects on abdominal aortic calcification (AAC) are uncertain. The present study comprehensively investigated the association between HbA1c and AAC in the 2013-2014 National Health and Nutrition Examinations Surveys.

METHODS

Among 1,799 participants ≥ 40 years, dual-energy X-ray absorptiometry-derived AAC was quantified using the Kauppila score (AAC-24). Severe AAC was defined as a total AAC-24 > 6. Weighted linear regression models and logistic regression models were used to determine the effects of HbA1c on AAC. The restricted cubic spline model was used for the dose-response analysis.

RESULTS

The mean AAC-24 of participants was 1.3, and 6.7% of them suffered from severe AAC. Both AAC-24 and the prevalence of severe AAC increased with the higher tertile of HbA1c (P < 0.001). Elevated HbA1c levels would increase the AAC-24 (β = 0.73, 95% CI: 0.30-1.16) and the risk of severe AAC (OR = 1.63, 95% CI: 1.29-2.06), resulting in nearly linear dose-response relationships in all participants. However, this positive correlation were not statistically significant when participants with diabetes were excluded. Furthermore, subgroup analysis showed significant interactions effect between HbA1c and hypertension on severe AAC with the OR (95% CI) of 2.35 (1.62-3.40) for normotensives and 1.39 (1.09-1.79) for hypertensives (P for interaction = 0.022).

CONCLUSION

Controlling HbA1c could reduce AAC scores and the risk of severe AAC. Glycemic management might be a component of strategies for preventing AAC among all participants, especially normotensives.

Adipokine-Cytokine Profile in Patients with Unstable Atherosclerotic Plaques and Abdominal Obesity

The goal of the research was to study the levels of adipokines and their associations with unstable atherosclerotic plaques in patients with coronary atherosclerosis and abdominal obesity (AO).

METHODS

The study included 145 men aged 38-79 with atherosclerosis of the coronary arteries (CA) and stable angina pectoris II-III FC who were hospitalized for coronary bypass surgery (2011-2022). The final analysis included 116 patients. Notably, 70 men had stable plaques in the CA (of which 44.3% had AO), and 46 men had unstable plaques in the CA (of which 43.5% had AO). Adipocytokine levels were determined using multiplex analysis (Human Metabolic Hormone V3 panel).

RESULTS

In the subgroup of patients with unstable plaques, patients with AO had a GLP-1 level that was 1.5 times higher and a lipocalin-2 level that was 2.1 times lower, respectively. GLP-1 is direct, and lipocalin-2 is inversely associated with AO in patients with unstable plaques. Among patients with AO, the level of lipocalin-2 in patients with unstable plaques was 2.2 times lower than in patients with stable plaques in the CA. The level of lipocalin-2 was inversely associated with the presence of unstable atherosclerotic plaques in the CA.

CONCLUSION

GLP-1 is directly associated with AO in patients with unstable atherosclerotic plaques. Lipocalin-2 is inversely associated with unstable atherosclerotic plaques in patients with AO.

Positive Association of Leptin and Artery Calcification of Lower Extremity in Patients With Type 2 Diabetes Mellitus: A Pilot Study

OBJECTIVE

We aimed to explore the role and possible mechanism of leptin in lower-extremity artery calcification in patients with type 2 diabetes mellitus (T2DM).

METHODS

We recruited 59 male patients with T2DM and 39 non-diabetic male participants. All participants underwent computed tomography scan of lower-extremity arteries. The calcification scores (CSs) were analyzed by standardized software. Plasma leptin level was determined by radioimmunoassay kits. Human vascular smooth muscle cells (VSMCs) calcification model was established by beta-glycerophosphate and calcium chlorideinduction. Calcium deposition and mineralization were measured by the o-cresolphthalein complexone method and Alizarin Red staining. The mRNA expression of bone morphogenic protein 2 (BMP2), runt-related transcription factor 2 (Runx2), osteocalcin (OCN) and osteopontin (OPN) was determined by quantitative RT-PCR. The protein levels of BMP2, Runx2, α-smooth muscle actin (α-SMA) and (p)-Akt was determined by Western-blot analysis, and α-SMA was also measured by immunofluorescence analysis.

RESULTS

Compared with controls, patients with T2DM showed higher median calcification score in lower-extremity artery [286.50 (IQR 83.41, 1082.00) vs 68.66 (3.41, 141.30), p<0.01]. Plasma leptin level was higher in patients with calcification score ≥300 than ≥100 (252.67 ± 98.57 vs 189.38 ± 44.19 pg/ml, p<0.05). Compared with calcification medium, intracellular calcium content was significantly increased in VSMCs treated by leptin (200, 400 and 800 ng/ml) combined with calcification medium [11.99 ± 3.63, 15.18 ± 4.55, and 24.14 ± 5.85 mg/ml, respectively, vs 7.27 ± 1.54 mg/ml, all p<0.01]. Compared with calcification medium, Alizarin Red staining showed calcium disposition was more obvious, and the mRNA level of BMP2, Runx2 and OCN was significantly increased, and immunofluorescence and Western blot analysis showed that the expression of α-SMA was downregulated in VSMCs treated by leptin (400 ng/ml) combined with calcification medium, respectively. Compared with calcification medium, the protein level of BMP2 and Runx2 was upregulated in VSMCs treated by leptin (400 ng/ml) combined with calcification medium. Moreover, blocking PI3K/Akt signaling pathway can decrease the protein expression of BMP2 and Runx2 in VSMCs treated by leptin (400 ng/ml) combined with calcification medium.

CONCLUSIONS

Leptin promoted lower-extremity artery calcification of T2DM by upregulating the expression of BMP2 and Runx2, and regulating phenotypic switch of VSMCs via PI3K/Akt signaling pathway.

Cardiorespiratory Fitness, Body Mass Index, and Markers of Insulin Resistance in Apparently Healthy Women and Men

BACKGROUND

Insulin resistance may be present in healthy adults and is associated with poor health outcomes. Obesity is a risk factor for insulin resistance, but most obese adults do not have insulin resistance. Fitness may be protective, but the association between fitness, weight, and insulin resistance has not been studied in a large population of healthy adults.

METHODS

A cross-sectional analysis of cardiorespiratory fitness, body mass index, and markers of insulin resistance was performed. Study participants were enrolled at the Cooper Clinic in Dallas, Texas. The analysis included 19,263 women and 48,433 men with no history of diabetes or cardiovascular disease. Cardiorespiratory fitness was measured using exercise treadmill testing. Impaired fasting glucose (100-125 mg/dL) and elevated fasting triglycerides (≥150 mg/dL) were used as a markers of insulin resistance.

RESULTS

Among individuals with normal weight, poor fitness was associated with 2.2-fold higher odds of insulin resistance in women (1.4-3.6; P = .001) and 2.8-fold higher odds in men (2.1-3.6; P <.001). The impact of fitness remained significant for overweight and obese individuals, with the highest risk group being the unfit obese. Among obese women, the odds ratio for insulin resistance was 11.0 for fit women (8.7-13.9; P <.001) and 20.3 for unfit women (15.5-26.5; P <.001). Among obese men, the odds ratio for insulin resistance was 7.4 for fit men (6.7-8.2; P < .001) and 12.9 for unfit men (11.4-14.6; P < .001).

CONCLUSIONS

Independent of weight, poor fitness is associated with risk of insulin resistance. Obese individuals, particularly women, may benefit from the greatest absolute risk reduction by achieving moderate fitness.

Superficial Femoral Artery Calcification Is a Novel Risk Factor of Microvascular Complications in T2DM Patients

Microvascular complications are prevalent in patients with type 2 diabetes mellitus (T2DM), resulting in increased risk of cardiovascular mortality. However, it is unclear whether above-knee artery calcification relates to microvascular complications. This study was aimed to investigate the role of calcification in superficial femoral arteries (SFA), the major above-knee artery, compared with anterior tibial arteries (ATA) and posterior tibial arteries (PTA), in T2DM-related microvascular complications and explore its risk factors. A single-center and observational study involving 359 T2DM patients was conducted. Clinical and laboratory data were collected. SFA calcification was evaluated by ultrasonography. Compared with ATA and PTA calcification, operating characteristics curve analysis showed that SFA calcification was the strongest predictor (63.1% sensitivity and 69.2% specificity) for T2DM-related microvascular complications (diabetic neuropathy, diabetic nephropathy and diabetic retinopathy). With the severity of SFA calcification increased, age, duration of T2DM, and SBP were significantly elevated, but triglyceride and glucose index and estimated glomerular filtration rate (eGFR) were significantly reduced (all P < 0.05). Multivariate logistic analysis showed that eGFR (OR 0.953; 95% CI 0.931-0.976; P < 0.001) was an independent risk factor of SFA calcification, especially in young patients with HbA1c > 7.0. We identified SFA calcification as a good predictor of microvascular complications in T2DM patients. Reduced eGFR was significantly associated with increased SFA calcification prevalence, especially in young T2DM patients with bad controlled hyperglycemia.

Insulin Resistance and Atherosclerosis: Implications for Insulin-Sensitizing Agents

Patients with type 2 diabetes mellitus (T2DM) are at high risk for macrovascular complications, which represent the major cause of mortality. Despite effective treatment of established cardiovascular (CV) risk factors (dyslipidemia, hypertension, procoagulant state), there remains a significant amount of unexplained CV risk. Insulin resistance is associated with a cluster of cardiometabolic risk factors known collectively as the insulin resistance (metabolic) syndrome (IRS). Considerable evidence, reviewed herein, suggests that insulin resistance and the IRS contribute to this unexplained CV risk in patients with T2DM. Accordingly, CV outcome trials with pioglitazone have demonstrated that this insulin-sensitizing thiazolidinedione reduces CV events in high-risk patients with T2DM. In this review the roles of insulin resistance and the IRS in the development of atherosclerotic CV disease and the impact of the insulin-sensitizing agents and of other antihyperglycemic medications on CV outcomes are discussed.

Atherosclerosis is a vascular stem cell disease caused by insulin

The present article proposes the hypothesis that when multipotent vascular stem cells are exposed to excessive insulin in a rhythmic pattern of sharply rising and falling concentrations, their differentiation is misdirected toward adipogenic and osteogenic cell lineages. This results in plaque-like accumulation of adipocytes with fat and cholesterol deposition from adipocyte debris, and osteogenic (progenitor) cells with a calcified matrix in advanced lesions. The ingrowth of capillaries and infiltration with macrophages, which upon uptake of lipids turn into foam cells, are unspecific pro-resolving reactions. Epidemiological, histopathological, pharmacological, and experimental evidence in favour of this hypothesis is summarised.

TG/HDL-C ratio and visceral adiposity index may be useful in assessment of insulin resistance in adults with type 1 diabetes in clinical practice

BACKGROUND

Insulin resistance (IR) is an important clinical issue in patients with type 1 diabetes due to worse metabolic control and risk of development of chronic complications.

OBJECTIVE

The aim of the study was to evaluate simple and easily available parameters as indirect markers of IR in adults with type 1 diabetes and correlate it with the results of hyperinsulinemic-euglycemic clamp.

METHODS

The study included 88 patients (62 men), aged 34.1 ± 6.5 years, with type 1 diabetes with a median disease duration of 8 (7-13) years and mean HbA1c of 7.6 ± 1.5%. Tissue sensitivity to insulin was assessed on the basis of glucose distribution rate (GDR) obtained in the course of hyperinsulinemic-euglycemic clamp. In addition, indirect markers of IR, such as estimated GDR, presence of features of metabolic syndrome, visceral adiposity index (VAI), and the triglyceride (TG)/high-density lipoprotein cholesterol (HDL-C) ratio, were evaluated.

RESULTS

In the study group, IR defined as GDR <4 mg/kg/min was observed in 33 (37.5%) patients. Group with IR had significantly higher postprandial glycemia (9.1 ± 2.0 vs 8.4 ± 1.1 mmol/L, P = .04), serum TG level (1.11 [0.75-1.92] vs 0.85 [0.60-1.08] mmol/L, P = .001), lower HDL-C level (1.59 ± 0.38 vs 1.8 ± 0.5 mmol/L, P = .02), higher TG/HDL-C ratio (1.60 [1.00-3.13] vs 1.05 [0.62-1.53], P = .001), and higher VAI (2.61 [1.31-4.25] vs 1.56 [0.96-2.25], P = .002). Significant relationship between GDR and TG/HDL-C ratio and VAI, adjusted for age, sex, HbA1c, and duration of diabetes was revealed (respectively, odds ratio 1.90 [95% confidence interval 1.15-3.15], P = .01 and odds ratio 1.47 [95% confidence interval 1.06-2.04], P = .01).

CONCLUSIONS

TG/HDL-C ratio and VAI appear to be clinically useful tools to assess IR in adults with type 1 diabetes.