Effects of an acute decrease in non-esterified fatty acid levels on muscle glucose utilization and forearm indirect calorimetry in lean NIDDM patients

Reversal and Remission of T2DM - An Update for Practitioners

Over the past 50 years, many countries around the world have faced an unchecked pandemic of obesity and type 2 diabetes (T2DM). As best practice treatment of T2DM has done very little to check its growth, the pandemic of diabesity now threatens to make health-care systems economically more difficult for governments and individuals to manage within their budgets. The conventional view has been that T2DM is irreversible and progressive. However, in 2016, the World Health Organization (WHO) global report on diabetes added for the first time a section on diabetes reversal and acknowledged that it could be achieved through a number of therapeutic approaches. Many studies indicate that diabetes reversal, and possibly even long-term remission, is achievable, belying the conventional view. However, T2DM reversal is not yet a standardized area of practice and some questions remain about long-term outcomes. Diabetes reversal through diet is not articulated or discussed as a first-line target (or even goal) of treatment by any internationally recognized guidelines, which are mostly silent on the topic beyond encouraging lifestyle interventions in general. This review paper examines all the sustainable, practical, and scalable approaches to T2DM reversal, highlighting the evidence base, and serves as an interim update for practitioners looking to fill the practical knowledge gap on this topic in conventional diabetes guidelines.

Nonesterified fatty acids and risk of sudden cardiac death in older adults

BACKGROUND

Although nonesterified fatty acids (NEFA) have been positively associated with coronary heart disease risk factors, limited and inconsistent data are available on the relation between NEFA and sudden cardiac death.

METHODS AND RESULTS

Using a prospective design, we studied 4657 older men and women (mean age, 75 years) from the Cardiovascular Health Study (1992-2006) to evaluate the association between plasma NEFA and the risk of sudden cardiac death in older adults. Plasma concentrations of NEFA were measured using established enzymatic methods, and sudden death was adjudicated using medical records, death certificates, proxy interview, and autopsy reports. We used Cox proportional hazard models to estimate multivariable-adjusted relative risks. During a median follow-up of 10.0 years, 221 new cases of sudden cardiac death occurred. In a multivariable model adjusting for age, sex, race, clinic site, alcohol intake, smoking, prevalent coronary heart disease and heart failure, and self-reported health status, relative risks (95% confidence interval) for sudden cardiac death were 1.0 (ref), 1.15 (0.81-1.64), 1.06 (0.72-1.55), and 0.91 (0.60-1.38) across consecutive quartiles of NEFA concentration. In secondary analyses restricted to the first 5 years of follow-up, we also did not observe a statistically significant association between plasma NEFA and sudden cardiac death.

CONCLUSIONS

Our data do not provide evidence for an association between plasma NEFA measured late in life and the risk of sudden cardiac death in older adults.

The second-meal phenomenon in type 2 diabetes

OBJECTIVE

In health, the rise in glucose after lunch is less if breakfast is eaten. We evaluated the second-meal effect in type 2 diabetes.

RESEARCH DESIGN AND METHODS

Metabolic changes after lunch in eight obese type 2 diabetic subjects were compared on 3 days: breakfast eaten, no breakfast, and no breakfast but intravenous arginine 1 h before lunch.

RESULTS

Despite comparable insulin levels, the rise in plasma glucose after lunch was considerably less if breakfast had been eaten (0.68 +/- 1.49 vs. 12.32 +/- 1.73 vs. 7.88 +/- 1.03 mmol x h(-1) x l(-1); P < 0.0001). Arginine administration almost halved the lunch rise in plasma glucose (12.32 +/- 1.73 vs. 7.88 +/- 1.03 mmol x h(-1) x l(-1)). The plasma free fatty acid concentration at lunchtime directly related to plasma glucose rise after lunch (r = 0.67, P = 0.0005).

CONCLUSIONS

The second-meal effect is preserved in type 2 diabetes. Premeal administration of a nonglucose insulin secretagogue results in halving the postprandial glucose rise and has therapeutic potential.

Orlistat in the prevention of diabetes in the obese patient

There has been an increase in the concern about preventing type 2 diabetes mellitus (T2DM), a disease with great and increasing prevalence. The prevalence of obesity, physical inactivity, Western processed diet, important risk factors for the development of T2DM, are also rising. Free fatty acids are increased in obesity and reduce insulin clearance and increase hepatic glucose production. Implementation of a healthy lifestyle has been show to slow the progression of impaired glucose tolerance to T2DM. Orlistat is an inhibitor of lipase activity, with proved efficacy in body weight reduction and long-term management of obesity and more favorable effects on carbohydrate metabolism and it was prospectively shown in XENDOS study that orlistat promoted long-term weight loss and prevented T2DM onset in obese individuals with normal and impaired glucose tolerance at baseline over four years. This benefit could be associated to the weight loss itself, to the limited absorption of lipids and reduction of plasma free fatty acids, to increased production of incretins or to modulation of secretion of cytokines by adipocytes, all effects secondary to orlistat treatment. A proposed strategy is to identify subjects at highest risk to receive a drug intervention, using lifestyle interventions alone at the community level.

Effects of moderate weight loss and orlistat on insulin resistance, regional adiposity, and fatty acids in type 2 diabetes

OBJECTIVE

Moderate weight loss is recommended for overweight and obese patients with type 2 diabetes, and conjunctive use of weight loss medication has been advocated. The current study examined weight loss-dependent and -independent effects of the intestinal lipase inhibitor orlistat at 6 months of treatment, using behavioral intervention (Int) combined with randomized, double-blinded, placebo (P)-controlled treatment with orlistat (O).

RESEARCH DESIGN AND METHODS

Metabolic control, insulin sensitivity (IS), regional fat distribution, and fat content in liver and muscle were measured in 39 volunteers with type 2 diabetes in whom all antidiabetic medication was withdrawn 1 month preceding randomization. Weight loss was equivalent in the Int+O and Int+P groups, respectively (-10.3 +/- 1.3 vs. -8.9 +/- 1.1%), and there were identical decreases in visceral adipose tissue (VAT), fat mass (FM), thigh adiposity, and hepatic steatosis.

RESULTS

Weight loss resulted in substantial improvement (P < 0.001) in HbA(1c) (-1.6 +/- 0.3 vs. -1.0 +/- 0.4%; NS between groups). IS improved significantly more with orlistat (Delta2.2 +/- 0.4 vs. Delta1.2 +/- 0.4 mg. min(-1). kg(-1) fat-free mass [FFM]; P < 0.05), and plasma free fatty acid (FFA) levels were strongly correlated with IS (r = 0.56; P < 0.001). Orlistat caused greater reductions in fasting plasma FFA (Delta-154 +/- 22 vs. Delta-51 +/- 33 micro mol/l; P < 0.05), insulin-suppressed FFA (Delta-119 +/- 23 vs. Delta-87 +/- 34 micro mol/l; P < 0.05), and fasting plasma glucose (FPG; -62 +/- 9 vs. -32 +/- 8 mg/dl; P = 0.02). Changes in HbA(1c) were correlated with DeltaIS (r = -0.41; P < 0.01) but not with weight loss per se.

CONCLUSIONS

At equivalent weight loss, conjunctive use of orlistat resulted in greater improvement in FFA levels and IS.

Acute intravenous L-arginine infusion decreases endothelin-1 levels and improves endothelial function in patients with angina pectoris and normal coronary arteriograms: correlation with asymmetric dimethylarginine levels

BACKGROUND

We tested the hypothesis that asymmetric dimethylarginine (ADMA) levels could be elevated and influence endothelin-1 and nitric oxide release and action in patients with cardiac syndrome X (CSX). In addition, we evaluated whether an intravenous infusion of L-arginine would improve endothelial function in these subjects.

METHODS AND RESULTS

Nine patients with CSX and 14 control subjects underwent a continuous infusion of L-arginine (0.125 g/min) or saline for 120 minutes. Sixty minutes after L-arginine or saline infusions, an intravenous insulin bolus (0.1 U/kg) combined with a euglycemic clamp was performed. Basal ADMA and endothelin-1 levels were higher in patients with CSX than in controls. At the end of the first hour of infusion, compared with saline, L-arginine infusion increased basal forearm blood flow, nitrite and nitrate (NOx), and forearm cGMP release and decreased endothelin-1. After insulin bolus, during saline, insulin-induced NOx, endothelin-1, and forearm cGMP release was almost abolished. Conversely, L-arginine restored a physiological profile of all endothelial variables compared with control subjects. In control subjects, compared with saline infusion, L-arginine infusion did not modify any parameter. ADMA levels were positively correlated with basal endothelin-1 levels and negatively correlated with insulin-induced incremental levels of NOx and forearm cGMP release.

CONCLUSIONS

Plasma ADMA levels are increased in patients with CSX, and they are correlated with increases in endothelin-1 and reductions in insulin-induced increments in plasma NOx and cGMP, effects that are reversed by intravenous L-arginine. These data suggest that increased ADMA levels play a role in the abnormal vascular reactivity that is observed in patients with CSX.

Acute lowering of circulating fatty acids improves insulin secretion in a subset of type 2 diabetes subjects

We tested the effects of acute perturbations of elevated fatty acids (FA) on insulin secretion in type 2 diabetes. Twenty-one type 2 diabetes subjects with hypertriglyceridemia (triacylglycerol >2.2 mmol/l) and 10 age-matched nondiabetic subjects participated. Glucose-stimulated insulin secretion was monitored during hyperglycemic clamps for 120 min. An infusion of Intralipid and heparin was added during minutes 60-120. In one of two tests, the subjects ingested 250 mg of Acipimox 60 min before the hyperglycemic clamp. A third test (also with Acipimox) was performed in 17 of the diabetic subjects after 3 days of a low-fat diet. Acipimox lowered FA levels and enhanced insulin sensitivity in nondiabetic and diabetic subjects alike. Acipimox administration failed to affect insulin secretion rates in nondiabetic subjects and in the group of diabetic subjects as a whole. However, in the diabetic subjects, Acipimox increased integrated insulin secretion rates during minutes 60-120 in the 50% having the lowest levels of hemoglobin A(1c) (379 +/- 34 vs. 326 +/- 30 pmol x kg(-1) x min(-1) without Acipimox, P < 0.05). A 3-day dietary intervention diminished energy from fat from 39 to 23% without affecting FA levels and without improving the insulin response during clamps. Elevated FA levels may tonically inhibit stimulated insulin secretion in a subset of type 2 diabetic subjects.

Disordered fat storage and mobilization in the pathogenesis of insulin resistance and type 2 diabetes

The primary genetic, environmental, and metabolic factors responsible for causing insulin resistance and pancreatic beta-cell failure and the precise sequence of events leading to the development of type 2 diabetes are not yet fully understood. Abnormalities of triglyceride storage and lipolysis in insulin-sensitive tissues are an early manifestation of conditions characterized by insulin resistance and are detectable before the development of postprandial or fasting hyperglycemia. Increased free fatty acid (FFA) flux from adipose tissue to nonadipose tissue, resulting from abnormalities of fat metabolism, participates in and amplifies many of the fundamental metabolic derangements that are characteristic of the insulin resistance syndrome and type 2 diabetes. It is also likely to play an important role in the progression from normal glucose tolerance to fasting hyperglycemia and conversion to frank type 2 diabetes in insulin resistant individuals. Adverse metabolic consequences of increased FFA flux, to be discussed in this review, are extremely wide ranging and include, but are not limited to: 1) dyslipidemia and hepatic steatosis, 2) impaired glucose metabolism and insulin sensitivity in muscle and liver, 3) diminished insulin clearance, aggravating peripheral tissue hyperinsulinemia, and 4) impaired pancreatic beta-cell function. The precise biochemical mechanisms whereby fatty acids and cytosolic triglycerides exert their effects remain poorly understood. Recent studies, however, suggest that the sequence of events may be the following: in states of positive net energy balance, triglyceride accumulation in "fat-buffering" adipose tissue is limited by the development of adipose tissue insulin resistance. This results in diversion of energy substrates to nonadipose tissue, which in turn leads to a complex array of metabolic abnormalities characteristic of insulin-resistant states and type 2 diabetes. Recent evidence suggests that some of the biochemical mechanisms whereby glucose and fat exert adverse effects in insulin-sensitive and insulin-producing tissues are shared, thus implicating a diabetogenic role for energy excess as a whole. Although there is now evidence that weight loss through reduction of caloric intake and increase in physical activity can prevent the development of diabetes, it remains an open question as to whether specific modulation of fat metabolism will result in improvement in some or all of the above metabolic derangements or will prevent progression from insulin resistance syndrome to type 2 diabetes.

Plasma fatty acids, adiposity, and variance of skeletal muscle insulin resistance in type 2 diabetes mellitus

Skeletal muscle insulin resistance (IR) is typically severe in type 2 diabetes mellitus (DM). However, the factors that account for interindividual differences in the severity of IR are not well understood. The current study was undertaken to examine the respective roles of plasma FFA, regional adiposity, and other metabolic factors as determinants of the severity of skeletal muscle IR in type 2 DM. Twenty-three subjects (12 women and 11 men) with type 2 DM underwent positron emission tomography imaging using [18F]2-fluoro-2-deoxyglucose during euglycemic insulin infusions (120 mU/min x m2) to measure skeletal muscle IR, using Patlak analysis of the tissue activity curves. Body composition analysis included body mass index, fat mass, and fat-free mass by dual energy x-ray tomography, and computed tomography determinations of visceral adiposity, thigh adipose tissue distribution, and muscle composition. Body mass index, fat mass, subfascial adiposity in the thigh, and visceral adipose tissue (VAT) were all significantly related to skeletal muscle IR (r = -0.48 to -0.63; P < 0.01). However, the strongest simple correlate of IR in skeletal muscle was insulin-suppressed plasma FFA (r = -0.81; P < 0.001). VAT was the sole component of adiposity that significantly correlated with insulin-suppressed plasma FFA concentration (r = 0.64; P < 0.001). These findings indicate that the severity of skeletal muscle IR in type 2 DM is closely related to the IR of suppressing lipolysis and that plasma fatty acids and VAT are key elements mediating the link between obesity and skeletal muscle IR in type 2 DM.

Physiological hyperinsulinemia impairs insulin-stimulated glycogen synthase activity and glycogen synthesis

Although chronic hyperinsulinemia has been shown to induce insulin resistance, the basic cellular mechanisms responsible for this phenomenon are unknown. The present study was performed 1) to determine the time-related effect of physiological hyperinsulinemia on glycogen synthase (GS) activity, hexokinase II (HKII) activity and mRNA content, and GLUT-4 protein in muscle from healthy subjects, and 2) to relate hyperinsulinemia-induced alterations in these parameters to changes in glucose metabolism in vivo. Twenty healthy subjects had a 240-min euglycemic insulin clamp study with muscle biopsies and then received a low-dose insulin infusion for 24 (n = 6) or 72 h (n = 14) (plasma insulin concentration = 121 +/- 9 or 143 +/- 25 pmol/l, respectively). During the baseline insulin clamp, GS fractional velocity (0.075 +/- 0.008 to 0.229 +/- 0.02, P < 0.01), HKII mRNA content (0.179 +/- 0.034 to 0.354 +/- 0.087, P < 0.05), and HKII activity (2.41 +/- 0.63 to 3.35 +/- 0.54 pmol x min(-1) x ng(-1), P < 0.05), as well as whole body glucose disposal and nonoxidative glucose disposal, increased. During the insulin clamp performed after 24 and 72 h of sustained physiological hyperinsulinemia, the ability of insulin to increase muscle GS fractional velocity, total body glucose disposal, and nonoxidative glucose disposal was impaired (all P < 0.01), whereas the effect of insulin on muscle HKII mRNA, HKII activity, GLUT-4 protein content, and whole body rates of glucose oxidation and glycolysis remained unchanged. Muscle glycogen concentration did not change [116 +/- 28 vs. 126 +/- 29 micromol/kg muscle, P = nonsignificant (NS)] and was not correlated with the change in nonoxidative glucose disposal (r = 0.074, P = NS). In summary, modest chronic hyperinsulinemia may contribute directly (independent of change in muscle glycogen concentration) to the development of insulin resistance by its impact on the GS pathway.