Glucose, insulin, diabetes and mechanisms of arterial dysfunction

Aging, vascular risk, and cognition: blood glucose, pulse pressure, and cognitive performance in healthy adults

Advanced age is associated with decline in many areas of cognition as well as increased frequency of vascular disease. Well-described risk factors for vascular disease, such as diabetes and arterial hypertension, have been linked to cognitive deficits beyond those associated with aging. To examine whether vascular health indices such as fasting blood glucose levels and arterial pulse pressure can predict subtle deficits in age-sensitive abilities, the authors studied 104 healthy adults (ages 18 to 78) without diagnoses of diabetes or hypertension. Whereas results revealed a classic pattern of age-related differences in cognition, preprandial blood glucose level and pulse pressure independently and differentially affected cognitive performance. High-normal blood glucose levels were associated with decreased delayed associative memory, reduced accuracy of working memory processing among women, and slower working memory processing among men. Elevated pulse pressure was associated with slower perceptual-motor processing. Results suggest that blood glucose levels and pulse pressure may be sensitive indicators of cognitive status in healthy adults; however, longitudinal research is needed to determine whether such relatively mild elevations in this select group predict age-related cognitive declines.

Imaging the tissue distribution of glucose in livers using a PARACEST sensor

Noninvasive imaging of glucose in tissues could provide important insights about glucose gradients in tissue, the origins of gluconeogenesis, or perhaps differences in tissue glucose utilization in vivo. Direct spectral detection of glucose in vivo by (1)H NMR is complicated by interfering signals from other metabolites and the much larger water signal. One potential way to overcome these problems is to use an exogenous glucose sensor that reports glucose concentrations indirectly through the water signal by chemical exchange saturation transfer (CEST). Such a method is demonstrated here in mouse liver perfused with a Eu(3+)-based glucose sensor containing two phenylboronate moieties as the recognition site. Activation of the sensor by applying a frequency-selective presaturation pulse at 42 ppm resulted in a 17% decrease in water signal in livers perfused with 10 mM sensor and 10 mM glucose compared with livers with the same amount of sensor but without glucose. It was shown that livers perfused with 5 mM sensor but no glucose can detect glucose exported from hepatocytes after hormonal stimulation of glycogenolysis. CEST images of livers perfused in the magnet responded to changes in glucose concentrations demonstrating that the method has potential for imaging the tissue distribution of glucose in vivo.

Insulin resistance: a proinflammatory state mediated by lipid-induced signaling dysfunction and involved in atherosclerotic plaque instability

The dysregulation of the insulin-glucose axis represents the crucial event in insulin resistance syndrome. Insulin resistance increases atherogenesis and atherosclerotic plaque instability by inducing proinflammatory activities on vascular and immune cells. This condition characterizes several diseases, such as type 2 diabetes, impaired glucose tolerance (IGT), impaired fasting glucose (IFG), obesity, hypertension, dyslipidemia, and other endocrinopathies, but also cancer. Recent studies suggest that the pathophysiology of insulin resistance is closely related to interferences with insulin-mediated intracellular signaling on skeletal muscle cells, hepatocytes, and adipocytes. Strong evidence supports the role of free fatty acids (FFAs) in promoting insulin resistance. The FFA-induced activation of protein kinase C (PKC) delta, inhibitor kappaB kinase (IKK), or c-Jun N-terminal kinase (JNK) modulates insulin-triggered intracellular pathway (classically known as PI3-K-dependent). Therefore, reduction of FFA levels represents a selective target for modulating insulin resistance.

Improvement of glycaemic control by nateglinide decreases systolic blood pressure in drug-naive patients with type 2 diabetes

BACKGROUND

It has been speculated that oral hypoglycaemic agents that block K-ATP channels could potentially increase blood pressure by blocking such channels in vascular myocytes. No information about this issue exists regarding nateglinide.

DESIGN

A multicentre, double-blind, placebo-controlled, randomized trial was conducted in 109 drug-naive 30- to 75-year-old patients with type 2 diabetes and < 5 years of diabetes diagnosis, who are not taking antihypertensive drugs. These patients were assigned to receive placebo or fixed doses of nateglinide (120 mg before each main meal: breakfast, lunch and dinner) and evaluated at weeks 0 and 12 for (i) body mass index and blood pressure; (ii) standard laboratory tests, including haemoglobin A1c (HbA1c) and fasting plasma glucose; and (iii) incremental area under the curve for glucose and C-peptide after a standardized liquid breakfast challenge, homeostasis model assessment (HOMA)-B% (as surrogate of beta-cell activity) and HOMA-S% (as surrogate of insulin sensitivity).

RESULTS

At the end of the follow-up period, patients in the nateglinide group (n = 55), compared to patients in the placebo group (n = 54), showed lower values of HbA1c (6.7 +/- 0.6 vs. 7.2 +/- 0.7%, respectively; P < 0.001), fasting plasma glucose (7.9 +/- 2.1 vs. 8.5 +/- 2.0 mmol L(-1); P = 0.023) and systolic blood pressure (125.3 +/- 15.4 vs. 129.3 +/- 18.7 mmHg; P = 0.015), and higher values of HOMA-B%[75.7 (51.8-99.4) vs. 57.7 (42.2-83.4); P = 0.033]. A positive correlation was found between changes in HbA1c and systolic blood pressure in the nateglinide group (r = 0.355, P = 0.011).

CONCLUSIONS

In drug-naive patients with type 2 diabetes, the improvement in glycaemic control with nateglinide is associated with a decrease in systolic blood pressure.

Manual therapy and cervical arterial dysfunction, directions for the future: a clinical perspective

This paper offers a contemporary, evidence-based perspective on the issue of adverse neurovascular events related to cervical spine manual therapy. The purpose of this perspective is to challenge traditional thought and practice and to recognize areas where practice and research should develop. By considering the themes presented in this paper, the clinician can broaden his or her approach to neurovascular assessment in line with contemporary evidence and thought. We present information based on clinically relevant questions. The nature of vertebrobasilar insufficiency and the utility of pre-treatment testing are examined in light of contemporary evidence. In addition, we report on internal carotid artery pathology, and the significance of appreciating atherosclerosis in clinical decision-making. These later two areas are not commonly recognized within manual therapy literature, and we suggest that their importance to differential diagnosis of head and neck pain, as well as estimating treatment related risk, is paramount. We propose that the term cervical arterial dysfunction is more appropriate than classically used nomenclature. This term refers more accurately and completely to the range of pathologies at different anatomical sites that manual therapists treating patients with head and neck pain are likely to encounter. Finally, we present a brief review of the medico-legal status pertaining to this area. Although this is English law-related, the themes derived from this section are of interest to all manual therapists.