Associations between insulin sensitivity, and free fatty acid and triglyceride metabolism independent of uncomplicated obesity

Comparison of Glycemic Excursion Using Flash Continuous Glucose Monitoring in Patients with Type 2 Diabetes Mellitus Before and After Treatment with Voglibose

Purpose: To determine the effect of Voglibose add-on therapy on daily glycemic excursions (using FreeStyle^® Libre Pro™, a Flash glucose monitoring system) in Indian patients with type 2 diabetes mellitus (T2DM) receiving a stable dose of metformin (Met) or metformin+sulfonylurea (Met+SU). Patients and Methods: T2DM patients with glycosylated hemoglobin (HbA1c) ≥7.0% and at least two postprandial excursions ≥140 mg/dL (within 2 h of meal) during the screening phase (visit 1/day -14 ± 2) were enrolled in this prospective, multicenter interventional study. The patients were randomized at visit 2 (day 0 ± 2) to receive Voglibose 0.2 or 0.3 mg tablets (BID/TID) as add-on therapy to Met and Met+SU. All the patients were followed at day 14 ± 2 (visit 3), month 3 ± 14 days (visit 4), 14 weeks (i.e., visit 4 + 14 days) ±2 days (visit 5), and month 6 ± 14 days (visit 6). Continuous glucose monitoring was performed to study glycemic excursions at visits 2, 3, and 5. The study outcomes were: change in average number of glycemic excursions per day, percent time spent in glucose fluctuations, mean Postprandial glucose (PPG), Fasting plasma glucose (FPG), day and night time mean glucose levels from baseline to day 14 and week 14; change in mean amplitude of glycemic excursion (MAGE) from baseline to 14 weeks; and mean HbA1c level at 3 and 6 months. Results: Out of 110 patients enrolled, 101 patients (91.8%) (Met+SU+Voglibose: 73 and Met+Voglibose: 28) completed the study. There was a significant decrease in average number of glycemic excursions per day from baseline to day 14 in the Met+Sul+Voglibose group and to week 14 in the Met+Voglibose group. There was also a significant reduction in percent time spent above target glucose range from baseline to day 14 in both treatment groups and to week 14 in the Met+SU+Voglibose group. A significant reduction in mean PPG area under the curve, day and night time mean glucose levels, and mean FPG levels from baseline to day 14 was reported in both treatment groups. A significant reduction in night time glucose, and average MAGE and HbA1c levels was reported from baseline to week 14 in the Met+Voglibose group and the Met+SU+Voglibose group, respectively. At 6 months, body weight, glucose levels, cholesterol, low-density lipoprotein-cholesterol, and HbA1c were significantly lower, especially in the Met+SU+Voglibose arm. Conclusion: Voglibose was useful in reducing glycemic variability and improving glycemic control in Asian Indian adults with T2DM. (CTRI/2018/04/013074).

I1-imidazoline receptor-mediated cardiovascular and metabolic effects in high-fat diet-induced metabolic syndrome in rats

OBJECTIVES

The objective of this study was to investigate the effects of a new I₁-imidazoline receptor-selective pyrroline compound on the hemodynamic, metabolic and microvascular alterations in a high-fat diet (HFD)-induced model of metabolic syndrome in rats.

METHODS

In total, twenty adult male Wistar rats were fed a high-fat diet (HFD, n = 20) for 20 weeks. Thereafter, the rats received a new pyrroline compound selective for I1-imidazoline receptors (LNP599; 10 mg/kg/day) or vehicle (n = 10/group) orally by gavage for 4 weeks. Functional microcirculation was assessed using intravital video microscopy, and structural microcirculation was evaluated using histochemical analysis.

RESULTS

LNP599 induced concomitant reductions in the SBP, HR and plasma catecholamine levels. The animals treated with this new antihypertensive compound also presented an improvement in body weight and the metabolic parameters related to metabolic syndrome, such as the glucose and lipid profiles. These effects were accompanied by a reversal of the functional and structural capillary rarefaction in the skeletal muscle.

CONCLUSIONS

The modulation of the sympathetic nervous system by a selective agonist for I₁-imidazoline receptors improves the hemodynamic and metabolic parameters in an experimental model of metabolic syndrome. LNP599 can also contribute to the restoration of microcirculatory parameters.

Impaired mitochondrial fatty acid oxidation and insulin resistance in aging: novel protective role of glutathione

Aging is associated with impaired fasted oxidation of nonesterified fatty acids (NEFA) suggesting a mitochondrial defect. Aging is also associated with deficiency of glutathione (GSH), an important mitochondrial antioxidant, and with insulin resistance. This study tested whether GSH deficiency in aging contributes to impaired mitochondrial NEFA oxidation and insulin resistance, and whether GSH restoration reverses these defects. Three studies were conducted: (i) in 82-week-old C57BL/6 mice, the effect of naturally occurring GSH deficiency and its restoration on mitochondrial (13) C1 -palmitate oxidation and glucose metabolism was compared with 22-week-old C57BL/6 mice; (ii) in 20-week C57BL/6 mice, the effect of GSH depletion on mitochondrial oxidation of (13) C1 -palmitate and glucose metabolism was studied; (iii) the effect of GSH deficiency and its restoration on fasted NEFA oxidation and insulin resistance was studied in GSH-deficient elderly humans, and compared with GSH-replete young humans. Chronic GSH deficiency in old mice and elderly humans was associated with decreased fasted mitochondrial NEFA oxidation and insulin resistance, and these defects were reversed with GSH restoration. Acute depletion of GSH in young mice resulted in lower mitochondrial NEFA oxidation, but did not alter glucose metabolism. These data suggest that GSH is a novel regulator of mitochondrial NEFA oxidation and insulin resistance in aging. Chronic GSH deficiency promotes impaired NEFA oxidation and insulin resistance, and GSH restoration reverses these defects. Supplementing diets of elderly humans with cysteine and glycine to correct GSH deficiency could provide significant metabolic benefits.

Obesity-related metabolic syndrome: mechanisms of sympathetic overactivity

The prevalence of the metabolic syndrome has increased worldwide over the past few years. Sympathetic nervous system overactivity is a key mechanism leading to hypertension in patients with the metabolic syndrome. Sympathetic activation can be triggered by reflex mechanisms as arterial baroreceptor impairment, by metabolic factors as insulin resistance, and by dysregulated adipokine production and secretion from visceral fat with a mainly permissive role of leptin and antagonist role of adiponectin. Chronic sympathetic nervous system overactivity contributes to a further decline of insulin sensitivity and creates a vicious circle that may contribute to the development of hypertension and of the metabolic syndrome and favor cardiovascular and kidney disease. Selective renal denervation is an emerging area of interest in the clinical management of obesity-related hypertension. This review focuses on current understanding of some mechanisms through which sympathetic overactivity may be interlaced to the metabolic syndrome, with particular regard to the role of insulin resistance and of some adipokines.

Obesity and adipokines: effects on sympathetic overactivity

Excess body weight is a major risk factor for cardiovascular disease, increasing the risk of hypertension, hyperglycaemia and dyslipidaemia, recognized as the metabolic syndrome. Adipose tissue acts as an endocrine organ by producing various signalling cytokines called adipokines (including leptin, free fatty acids, tumour necrosis factor-α, interleukin-6, C-reactive protein, angiotensinogen and adiponectin). A chronic dysregulation of certain adipokines can have deleterious effects on insulin signalling. Chronic sympathetic overactivity is also known to be present in central obesity, and recent findings demonstrate the consequence of an elevated sympathetic outflow to organs such as the heart, kidneys and blood vessels. Chronic sympathetic nervous system overactivity can also contribute to a further decline of insulin sensitivity, creating a vicious cycle that may contribute to the development of the metabolic syndrome and hypertension. The cause of this overactivity is not clear, but may be driven by certain adipokines. The purpose of this review is to summarize how obesity, notably central or visceral as observed in the metabolic syndrome, leads to adipokine expression contributing to changes in insulin sensitivity and overactivity of the sympathetic nervous system.

Mixed meal modeling and disturbance rejection in type I diabetic patients

A mixed meal model was developed to capture the gut absorption of glucose, protein, and free fatty acid (FFA) from a mixed meal into the circulatory system. The output of the meal model served as a disturbance to the extended minimal model, which successfully captured plasma FFA, glucose and insulin concentration dynamics and interactions. A model predictive controller (MPC) was synthesized to reject meal disturbances and maintain normoglycemia. The dynamic fit of blood glucose after mixed meal consumption was consistent with the published data. The results from the closed-loop simulations were also promising; the MFC was able to maintain the glucose concentration within the normoglycemic range during and after consumption of a mixed meal.

Impact of steatosis on insulin secretion in chronic hepatitis C patients

OBJECTIVES

Liver steatosis is frequently observed in patients with chronic hepatitis C (CHC) and is an identified risk factor for progression of liver fibrosis. This study aimed to evaluate the relationship between steatosis and host/viral factors, and the correlation between steatosis and insulin secretion in CHC patients with normal glucose tolerance (NGT).

METHODS

A total of 212 CHC patients were enrolled in this study. Insulin resistance and insulin secretion were determined in response to oral loading of 75 g glucose. Liver fibrosis and steatosis were quantified by the image analysis.

RESULTS

Of the 212 CHC patients, 165 (78%) had steatosis, mostly of a mild degree. Multiple ordinal regression analysis revealed body mass index (BMI) (P= 0.011) as the main factor associated with severe steatosis. Of the 212 CHC patients, 148 (61%) showed NGT, and the serum insulin response to oral glucose loading in these NGT patients with steatosis was significantly different from that in patients with NGT but no steatosis. The peak insulin response occurred at 60 min in cases of mild steatosis, and at 90 min in patients with moderate or severe steatosis. The insulin level at 120 min in patients with severe steatosis was higher than that in those without steatosis. The total area under the response curve of insulin during OGTT in the patients with steatosis is higher than that in those without steatosis.

CONCLUSION

Exaggerated insulin secretion was observed even in CHC patients with mild steatosis and NGT, suggesting the presence of insulin resistance. Exaggerated insulin secretion may accelerate the progression of liver fibrosis in CHC patients.

Single‐ or Double‐Blind Treatment With Balsamodendron tnukul and Nifedipine in Hypertensive Patients

This study assessed and compared the effects of Balsamodendron mukul (an extract of the gum of a small tree) and nifedipine (a calcium-channel-blocking reference drug) on blood pressure, lipids, lipoproteins, and phospholipids in randomly selected patients with essential hypertension. Fifty-seven newly diagnosed hypertensive patients were randomly divided into three groups. They received either single-blind B. mukul (1.5 g/d) or single-blind nifedipine (10 mg/d) double-blind therapy with nifedipine (10 mg/d) and B. mukul (1.5 g/d) for 6 weeks. These groups were compared with control subjects. On treatment with B. mukul, levels of systolic blood pressure, diastolic blood pressure, plasma total cholesterol, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol, triglycerides, free fatty acids, and phospholipid levels were significantly reduced, and high-density lipoprotein cholesterol levels were significantly elevated, as compared with untreated hypertensive patients. Combined therapy with B. mukul and nifedipine was more beneficial than the treatment with B. mukul alone. Our study suggests that B. mukul may be an effective antihypertensive and hypolipidemic agent.

Dynamic modeling of free fatty acid, glucose, and insulin: an extended "minimal model"

BACKGROUND

The mathematical models for patients with diabetes proposed in the literature since the late 1970s are mainly glucocentric (glucose-based); hence, the contribution of free fatty acid (FFA) metabolism in the body and its glucose-insulin interactions have been largely ignored. However, approximately 90% of the muscle energy is derived from FFA metabolism when the body is at rest. Furthermore, significant interactions exist among FFA, glucose, and insulin. With the long-term goal of developing a closed-loop glucose control system, a model of the major energy-providing substrate dynamics is required.

METHODS

The Bergman minimal model was extended to include plasma FFA dynamics, and its interaction with glucose and insulin dynamics, with a primary focus on patients with Type 1 diabetes. Differential equations were developed for plasma FFA concentrations and "remote" FFA effects on glucose uptake, as well as "remote" insulin effects on plasma FFA concentrations. Parameters for the model were estimated from experimental data provided in the scientific literature.

RESULTS

The minimal model was extended in order to capture three major metabolic aspects: the antilipolytic effect of insulin; the lipolytic effect of prolonged hyperglycemia; and the impairing effect of FFA on glucose uptake rate. The dynamic fit of glucose, FFA, and insulin profiles is consistent with published data.

CONCLUSIONS

The extended minimal model successfully captured the plasma FFA concentration behavior, the plasma insulin and glucose concentrations, and the physiological interactions that exist among these species. This more comprehensive description of energy-providing substrate dynamics may provide a novel simulation test-bed for analysis of patients with insulin dependent diabetes and controller design.

Inhibition of the renin-angiotensin system prevents free fatty acid-induced acute endothelial dysfunction in humans

OBJECTIVE

An elevated free fatty acid (FFA) level impairs endothelium-dependent vasodilation in humans, which may be pathophysiologically relevant to the development of endothelial dysfunction in patients with insulin resistance. We investigated the effect of inhibition of the renin-angiotensin system (RAS) on FFA-induced endothelial dysfunction.

METHODS AND RESULTS

Changes in forearm blood flow during intra-arterial infusion of acetylcholine were measured by plethysmography before and after systemic infusion of lipid/heparin in 10 healthy subjects given a single dose of placebo, losartan (50 mg), or perindopril (8 mg). Endothelial function after lipid/heparin infusion was also investigated with the coinfusion of vitamin C or NG-monomethyl-L-arginine (L-NMMA). Elevated FFA significantly reduced the response to acetylcholine by 37.7% (P=0.0096) without L-NMMA, but not the response with L-NMMA, whereas FFA did not affect the response to nitroprusside. The single dose of either losartan or perindopril completely prevented FFA-induced endothelial dysfunction. Vitamin C also prevented FFA-induced endothelial dysfunction.

CONCLUSIONS

Elevated FFA levels by lipid/heparin infusion, which may partly mimic the abnormal lipid profile in patients with insulin resistance, caused endothelial dysfunction via RAS activation and the presumably resultant oxidative stress in humans. Our results suggest the therapeutic rationale for RAS inhibition in patients with high FFA levels.

Insulin resistance as putative cause of chronic renal transplant dysfunction

Transplantation is the preferred organ replacement therapy for most patients with end-stage renal disease. Despite impressive improvements over recent years in the treatment of acute rejection, approximately half of all grafts will loose function within 10 years after transplantation. Chronic renal transplant dysfunction, also known as transplant atherosclerosis, is a leading cause of late allograft loss. To date, no specific treatment for chronic renal transplant dysfunction is available. Although its precise pathophysiology remains unknown, it is believed that it involves a multifactorial process of alloantigen-dependent and alloantigen-independent risk factors. Obesity, posttransplant diabetes mellitus, dyslipidemia, hypertension, and proteinuria have all been identified as alloantigen-independent risk factors. Notably, these recipient-related risk factors are well-known risk factors for cardiovascular disease, which cluster within the insulin resistance syndrome in the general population. Insulin resistance is considered the central pathophysiologic feature of this syndrome. It is therefore tempting to speculate that it is insulin resistance that underlies the recipient-related risk factors for chronic renal transplant dysfunction. Recognition of insulin resistance as a central feature underlying many, if not all, recipient-related risk factors would not only improve our understanding of the pathophysiology of chronic renal transplant dysfunction, but also stimulate development of new treatment and prevention strategies.

Exercise training, without weight loss, increases insulin sensitivity and postheparin plasma lipase activity in previously sedentary adults

OBJECTIVE

To determine the effects of exercise, without weight loss, on insulin sensitivity (S(I)), postheparin plasma lipase activity (PHPL), intravenous fat clearance rate (K(2)), and fasting lipids in sedentary adults.

RESEARCH DESIGN AND METHODS

At baseline and after 6 months of walk training (intensity 45-55 or 65-75% heart rate reserve, frequency 3-4 or 5-7 days/week, duration 30 min/session), anthropometric indexes, S(I), PHPL, K(2), and fasting lipids were measured in 18 sedentary adults (12 women, 6 men; 51.9 +/- 5.8 years of age, BMI 28.9 +/- 4.6 kg/m(2)).

RESULTS

Exercise increased S(I) (2.54 +/- 2.74 vs. 4.41 +/- 3.30 microU ml(-1) x min(-1), P < 0.005) and both lipoprotein lipase (LPL) (1890 +/- 1380 vs. 4926 +/- 1858 nEq free fatty acid [FFA]. ml(-1). h(-1)) and hepatic lipase (HL) activities (3326 +/- 1605 vs. 4636 +/- 1636 nEq FFA. ml(-1) x h(-1)) (both P < 0.001), without altering BMI, waist circumference, K(2), or fasting lipids. Correlations between changes in LPL and the total:HDL cholesterol ratio (r = -0.54) and changes in the LPL:HL ratio and waist circumference (r = -0.50) were significant (P < 0.05).

CONCLUSIONS

Exercise, without weight loss, increases S(I) and PHPL activity in previously sedentary adults, without changing K(2) or fasting lipid levels. Furthermore, increased LPL is associated with a decreased total:HDL ratio, and an increased LPL:HL ratio is associated with a decreased waist circumference. Therefore, even modest amounts of exercise in the absence of weight loss positively affect markers of glucose and fat metabolism in previously sedentary, middle-aged adults.

Dietary restriction and glucose regulation in aging rhesus monkeys: a follow-up report at 8.5 yr

In a longitudinal study of the effects of moderate (70%) dietary restriction (DR) on aging, plasma glucose and insulin concentrations were measured from semiannual, frequently sampled intravenous glucose tolerance tests (FSIGTT) in 30 adult male rhesus monkeys. FSIGTT data were analyzed with Bergman's minimal model, and analysis of covariance revealed that restricted (R) monkeys exhibited increased insulin sensitivity (S(I), P < 0.001) and plasma glucose disappearance rate (K(G), P = 0.015), and reduced fasting plasma insulin (I(b), P < 0.001) and insulin response to glucose (AIR(G), P = 0.023) compared with control (C; ad libitum-fed) monkeys. DR reduced the baseline fasting hyperinsulinemia of two R monkeys, whereas four C monkeys have maintained from baseline, or subsequently developed, fasting hyperinsulinemia; one has progressed to diabetes. Compared with only the normoinsulinemic C monkeys, R monkeys exhibited similarly improved FSIGTT and minimal-model parameters. Thus chronic DR not only has protected against the development of insulin resistance in aging rhesus monkeys, but has also improved glucoregulatory parameters compared with those of otherwise normoinsulinemic monkeys.

Free fatty acids/triglycerides increase ocular and subcutaneous blood flow

Elevated plasma free fatty acids (FFA) induce skeletal muscle insulin resistance and impair endothelial function. The aim of this study was to characterize the acute hemodynamic effects of FFA in the eye and skin. A triglyceride (Intralipid 20%, 1.5 ml/min)/heparin (bolus: 200 IU; constant infusion rate: 0.2 IU. kg(-1). min(-1)) emulsion or placebo was administered to 10 healthy subjects. Measurements of pulsatile choroidal blood flow with laser interferometry, retinal blood flow with the blue field entoptic technique, peak systolic and end diastolic blood velocity (PSV, EDV) in the ophthalmic artery with Doppler sonography, and subcutaneous blood flow with laser Doppler flowmetry were performed during an euglycemic somatostatin-insulin clamp over 405 min. Plasma FFA/triglyceride elevation induced a rise in pulsatile choroidal blood flow by 25 +/- 3% (P < 0.001) and in retinal blood flow by 60 +/- 23% (P = 0.0125). PSV increased by 27 +/- 8% (P = 0.001), whereas EDV was not affected. Skin blood flow increased by 149 +/- 38% (P = 0.001). Mean blood pressure and pulse rate remained unchanged, whereas pulse pressure amplitude increased by 17 +/- 5% (P = 0.019). Infusion of heparin alone had no hemodynamic effect in the eye or skin. In conclusion, FFA/triglyceride elevation increases subcutaneous and ocular blood flow with a more pronounced effect in the retina than in the choroid, which may play a role for early changes of ocular perfusion in the insulin resistance syndrome.

Liver steatosis in juvenile obesity: correlations with lipid profile, hepatic biochemical parameters and glycemic and insulinemic responses to an oral glucose tolerance test

OBJECTIVE

The aim of this study was to evaluate liver steatosis in prepubertal and pubertal obese and the correlations with the lipid profile, the serum levels of hepatic parameters and the glycemic and insulinemic responses to an oral glucose tolerance test.

SUBJECTS

375 obese, 205 males and 170 females, Tanner pubertal stage I (n=82), stages II-III (n=80) and stages IV-V (n=213).

MEASUREMENTS

Body mass index (BMI), waist-hip ratio (WHR), total cholesterol and high density lipoprotein (HDL), cholesterol/HDL ratio, low density lipoprotein (LDL), very low density lipoprotein (VLDL), triglycerides (TGL), aspartate aminotransferase (AST), alanine aminotransferase (ALT), gGT, glycemia (G), insulinemia (IRI), fasting IRI/G ratio (FIGR), glycemic (mean blood glucose, MBG) and insulinemic (mean serum insulin, MSI) responses during a 120 min oral glucose tolerance test (OGTT), expressed as area under the curve (AUC)/120 min, pancreatic insulinemic response to glucose (IRG), and liver ultrasound scanning for assessing the degree of steatosis (moderate, severe).

RESULTS

Liver steatosis was found in 33% of subjects in Tanner pubertal stage I, 36% in stage II-III and 47% in stages IV-V. BMI and transaminases were correlated with the degree of steatosis in all pubertal stages. AST, ALT and gGT were higher in the presence of steatosis, while elevated TGL was present in late puberty only; however the increase of ALT is specific for steatosis.

CONCLUSION

Juvenile obesity involves a high risk of liver steatosis associated with alterations of transaminases and lipid but not glucose metabolism. These changes are apparent even to the prepubertal stage.

Relation of plasma lipids to insulin resistance, nonesterified fatty acid levels, and body fat in men from three ethnic groups: relevance to variation in risk of diabetes and coronary disease

Afro-Caribbean men in the United Kingdom have a favorable lipoprotein profile and are at low risk of coronary heart disease (CHD) compared with Europeans and South Asians, but are at high risk of non-insulin-dependent diabetes mellitus (NIDDM) compared with Europeans. To investigate these differences, a cross-sectional comparison was undertaken for measures of lipoprotein metabolism, body composition, and insulin's glucoregulatory and antilipolytic actions in 92 healthy men (42 to 61 years) of Afro-Caribbean, South Asian, or European origin. Afro-Caribbean men were more insulin-resistant than Europeans (insulin sensitivity [Si], 1.96 v3.01 min(-1) x microU(-1) x mL, P < .01). They nevertheless had a more favorable lipoprotein profile, with lower levels of very-low-density lipoprotein (VLDL) cholesterol (0.21 v 0.40 mmol/L, P < .01) and triglycerides (0.34 v 0.74 mmol/L, P < .01), lower serum total triglycerides, higher high-density lipoprotein 2 (HDL2) cholesterol, and larger low-density lipoprotein (LDL) particle size. These differences were not accounted for by differences in nonesterified fatty acid (NEFA) levels, the sensitivity of suppression of NEFA levels to insulin, or body composition. South Asians were also more insulin-resistant than Europeans but had a less favorable lipoprotein profile. Afro-Caribbean men in the United Kingdom are as insulin-resistant as South Asian men but less susceptible to the lipid disturbances that characteristically accompany insulin resistance. This favorable lipid pattern may relate to more effective VLDL metabolism rather than a reduced supply of NEFA as substrate for triglyceride synthesis.

Severe hyperlipidemia in apolipoprotein E2 homozygotes due to a combined effect of hyperinsulinemia and an SstI polymorphism

More than 90% of patients with type III hyperlipoproteinemia are homozygous carriers of the apolipoprotein (apo) E*2 allele. The great majority of these apoE2(Arg158-->Cys) homozygotes in the general population, however, are normolipidemic. Apparently, expression of the hyperlipidemic state requires additional genetic and/or environmental factors, suggesting a multifactorial etiology. To elucidate these additional risk factors, we analyzed normolipidemic and hyperlipidemic apoE2 homozygotes. Hyperinsulinemia was observed in 27 of 49 apoE2 homozygotes and associated with elevated lipid levels: hyperinsulinemic apoE2 homozygotes had type III hyperlipoproteinemia 6 times more often than apoE2 homozygotes with normal insulin levels (odds ratio 6.2, P=0.02). We screened the normolipidemic and hyperlipidemic apoE2 homozygotes for common variants in candidate genes involved in lipolysis-the APOA1-C3-A4 gene cluster, lipoprotein lipase, and hepatic lipase-and analyzed for associations with the expression of hyperlipidemia. In the hyperinsulinemic group, the 7 carriers of the SstI polymorphism (S2) in the APOC3 gene displayed severely elevated VLDL cholesterol (P(insulin by SstI)<0.001) and VLDL triglyceride (P(insulin by SstI)<0.01) and low levels of HDL (P(insulin by SstI)<0.02). In the normoinsulinemic group, no such relation of the SstI polymorphism with hyperlipidemia was observed. These data provide the first evidence for a combined effect of hyperinsulinemia and the SstI polymorphism on the expression of hyperlipidemia in apoE2 homozygotes.

Screening for cardiovascular disease. Concepts, conflicts, and consensus

CVD in the United States is prevalent, costly, and disabling. Wherever in the arterial tree atherosclerosis occurs, the process appears to begin in youth, to develop under the influence of the same risk factors, and to be amenable to the same interventions. The relationship between CVD and its associated risk factors is continuous, is graded, and extends below thresholds previously defined as normal. This observation, in turn, is based on an appreciation that in our society, the gap between normal and optimal can be considerable. CVD is a multifactorial process, often related to modifiable lifestyle choices; we focus on any single risk factor to the exclusion of others puts patients in danger. Because risk factors rarely occur in isolation, risk assessment must be as multifactorial as the underlying disease process. By understanding differences between risk factors in terms of the impact of their modification on the underlying disease, targeted interventions become possible that are tailored to the likelihood of an individual patient acquiring CVD. To change the overall prevalence of an epidemic disease such as CVD, however, such a high-risk approach must be applied in concert with a population strategy that seeks to effect smaller degrees of change in the large segment of society that may be at only moderate risk but--because of their great numbers--bears most of the morbidity and mortality of CVD. Finally, despite the remarkable progress that has been made in our understanding of the pathophysiology of CVD and the effectiveness of risk factor modification, significant gaps remain between knowledge and behavior. Fewer than 50% of diabetics are even aware that they have the disease. Only a third of those whose lipid levels qualify them for treatment receive intervention of any kind, including dietary advice. Only 27% of hypertensives have their blood pressure adequately controlled. The potential impact of more vigorous screening practices in the primary care setting on the health of individuals and communities cannot be overstated.

Hypertriglyceridemia, atherogenic dyslipidemia, and the metabolic syndrome

The importance of high serum cholesterol, especially a high level of low-density lipoprotein (LDL) cholesterol, as a risk factor for coronary artery disease is well established. Likewise, efficacy for decreasing risk for coronary artery disease by LDL-lowering therapy has recently been documented through clinical trials. However, many high-risk patients manifest elevated serum triglyceride levels, and the role of hypertriglyceridemia in causation of coronary artery disease remains to be elucidated. Nonetheless, there is growing evidence that hypertriglyceridemia is a marker for increased risk for coronary artery disease; in fact, it can serve as a marker for several atherogenic factors. These factors include increased concentrations of atherogenic triglyceride-rich lipoproteins; the atherogenic lipoprotein phenotype, or lipid triad; and the metabolic syndrome. The lipid triad consists of elevated serum triglycerides, small LDL particles, and low high-density lipoprotein (HDL) cholesterol. The metabolic syndrome includes the coexistence of the lipid triad, elevated blood pressure, insulin resistance (plus glucose intolerance), and a prothrombotic state. Many previous studies indicate that hypertriglyceridemia is strongly associated with all of these atherogenic factors. The clinical approach to treatment of patients with hypertriglyceridemia thus requires a broad-based strategy that includes reduction of atherogenic triglyceride-rich lipoproteins, reversal of the lipid triad, and favorable modification of the metabolic syndrome. The development of therapeutic regimens to effect these changes poses a challenge for future research on the problem of hypertriglyceridemia.

Elevated circulating free fatty acid levels impair endothelium-dependent vasodilation

We have recently shown that insulin-resistant obese subjects exhibit impaired endothelial function. Here, we test the hypothesis that elevation of circulating FFA to levels seen in insulin-resistant subjects can impair endothelial function. We studied leg blood flow responses to graded intrafemoral artery infusions of the endothelium-dependent vasodilator methacholine chloride (Mch) or the endothelium-independent vasodilator sodium nitroprusside during the infusion of saline and after raising systemic circulating FFA levels exogenously via a low- or high-dose infusion of Intralipid plus heparin or endogenously by an infusion of somatostatin (SRIF) to produce insulinopenia in groups of lean healthy humans. After 2 h of infusion of Intralipid plus heparin, FFA levels increased from 562+/-95 to 1,303+/-188 micromol, and from 350+/-35 to 3,850+/-371 micromol (P < 0.001) vs. saline for both low- and high-dose groups, respectively. Mch-induced vasodilation relative to baseline was reduced by approximately 20% in response to the raised FFA levels in both groups (P < 0.05, saline vs. FFA, ANOVA). In contrast, similar FFA elevation did not change leg blood flow responses to sodium nitroprusside. During the 2-h SRIF infusion, insulin levels fell, and FFA levels rose from 474+/-22 to 1,042+/-116 micromol (P < 0.01); Mch-induced vasodilation was reduced by approximately 20% (P < 0.02, saline vs. SRIF, ANOVA). Replacement of basal insulin levels during SRIF resulted in a fall of FFA levels from 545+/-47 to 228+/-61 micromol, and prevented the impairment of Mch-induced vasodilation seen with SRIF alone. In conclusion, (a) elevated circulating FFA levels cause endothelial dysfunction, and (b) impaired endothelial function in insulin-resistant humans may be secondary to the elevated FFA concentrations observed in these patients.

Clara cell protein correlation with hyperlipidemia

Serum levels of protein 1 (P1), a Clara cell secretory protein, in 746 healthy subjects were measured and their correlations with different types of serum lipids and lipoproteins-that is, triglyceride (TG), total cholesterol (TCh), free cholesterol (FCh), high-density lipoprotein (HDL), low-density lipoprotein (LDL), and apoproteins (apo) A-I, A-II, and B-were examined. P1 serum levels were examined for their correlation with body mass index (BMI), and were compared for 47 obese, 70 normal, and 17 lean males. P1 serum levels in 69 patients with diabetes mellitus and 24 patients with atherosclerotic stenosis of the carotid artery or coronary artery were also compared to those in healthy control subjects. P1 showed a significant positive correlation with TG, TCh, FCh, apo A-I, apo A-II, apo B, and BMI (r = 0.93, 0.26, 0.42, 0.11, 0.35, 0.58, and 0.20, respectively; p < 0.0001 to 0.05), and an inverse correlation with HDL (r = -0.32; p < 0.01). P1 values in obese men (mean +/- SD: 139.2 +/- 98.2 micrograms/L) were significantly higher than those in normal (90.3 +/- 57.1) and lean ones (65.6 +/- 40.8) (p < 0.01). In both diabetic and atherosclerotic patients, P1 serum levels did not significantly differ from those in healthy subjects. From these results, we conclude the following: (1) the serum levels of P1 correlate significantly with those of lipids and lipoproteins; (2) P1 serum levels increase in the case of obesity.

Reduced glucose effectiveness associated with reduced insulin release: an artifact of the minimal-model method

We previously demonstrated that minimal model-derived estimates of glucose effectiveness (SG), based on the frequently sampled intravenous glucose tolerance test (SGFSIGT), were reduced in islet-transplanted or streptozotocin-treated dogs and in patients with insulin-dependent diabetes mellitus. To ascertain the validity of our observations, we compared SGFSIGT with estimates based on a basal hormone replacement glucose clamp (SGBRCLAMP) and a basal hormone replacement glucose tolerance test (SGBRGTT) in normal control (CNTL, n = 12) and streptozotocin-treated dogs with normal fasting plasma glucose (STZ-Rx, n = 9). SGFSIGT was reduced in STZ-Rx compared with CNTL (P < 0.05). However, neither SGBRCLAMP nor SGBRGTT was reduced in the STZ-Rx group (P > 0.05). Comparison of protocols for each subject indicated that SGFSIGT was greater than either SGBRCLAMP or SGBRGTT in control (P < 0.002) but not in STZ-Rx dogs (P > 0.1). The relationship of SGFSIGT to insulin secretory function suggests that our previous conclusion that SGFSIGT was reduced in subjects with limited insulin release may be an artifact of the minimal-model method. Our results suggest that caution must be exercised in the interpretation of differences in minimal-model estimates of SG between subject groups with significantly different levels of insulin secretory function.