Efficacy and safety of empagliflozin, a sodium glucose cotransporter 2 (SGLT2) inhibitor, as add-on to metformin in type 2 diabetes with mild hyperglycaemia

AIMS

To evaluate the effects of the sodium glucose cotransporter 2 (SGLT2) inhibitor empagliflozin added to metformin for 12 weeks in patients with type 2 diabetes.

METHODS

This dose-ranging, double-blind, placebo-controlled trial randomized 495 participants with type 2 diabetes inadequately controlled on metformin [haemoglobin A1c (HbA1c) >7 to ≤10%] to receive 1, 5, 10, 25, or 50 mg empagliflozin once daily (QD), or placebo, or open-label sitagliptin (100 mg QD), added to metformin for 12 weeks. The primary endpoint was change in HbA1c from baseline to week 12 (empagliflozin groups versus placebo).

RESULTS

Reductions in HbA1c of -0.09 to -0.56% were observed with empagliflozin after 12 weeks, versus an increase of 0.15% with placebo (baseline: 7.8-8.1%). Compared with placebo, empagliflozin doses from 5 to 50 mg resulted in reductions in fasting plasma glucose (-2 to -28 mg/dl vs. 5 mg/dl with placebo; p < 0.0001) and body weight (-2.3 to -2.9 kg vs. -1.2 kg; p < 0.01). Frequency of adverse events was generally similar with empagliflozin (29.6-48.6%), placebo (36.6%) and sitagliptin (35.2%). Hypoglycaemia rates were very low and balanced among groups. Most frequent adverse events with empagliflozin were urinary tract infections (4.0% vs. 2.8% with placebo) and pollakiuria (2.5% vs. 1.4% with placebo). Genital infections were reported only with empagliflozin (4.0%).

CONCLUSIONS

Once daily empagliflozin as add-on therapy to metformin was well tolerated except for increased genital infections and resulted in reductions in HbA1c, fasting plasma glucose and body weight in patients with type 2 diabetes inadequately controlled on metformin monotherapy.

Comparison of fasting and postprandial plasma lipoproteins in subjects with and without coronary heart disease

Plasma lipoprotein levels, including remnant-like particle (RLP) cholesterol and RLP triglycerides, were assessed in fasting (12 hours) and postprandial (PP) (4 hours after a fat-rich meal) states in 88 patients with coronary heart disease (CHD) and 88 controls. All lipoproteins were assessed by direct methods. We hypothesized that patients with CHD would have greater percent increases in their triglyceride levels, RLP cholesterol, and RLP triglycerides, in response to a fat-rich meal. In the fasting state, triglycerides, RLP cholesterol, RLP triglycerides, and low-density lipoprotein (LDL) cholesterol levels were all significantly higher in cases versus controls by 51%, 35%, 39%, and 40%, respectively. These levels were 57%, 37%, 64%, and 37% higher in the PP state, respectively. Mean high-density lipoprotein (HDL) cholesterol values were 27% lower in cases in both the fasting and PP states. After eating, triglycerides, RLP cholesterol, and RLP triglycerides increased 64%, 71%, and 290% in controls, respectively, whereas in cases these levels increased by 71%, 94%, and 340%, respectively (all p <0.0001). Percent increases in the PP state were not significantly different in cases versus controls. Following the fat-rich meal, LDL and HDL cholesterol decreased by 5% and 4% in controls, and by 7% and 6% in patients, with no significant difference in percent changes between groups. Fasting values correlated very highly with PP values for all parameters (all p <0.0001). Our data indicate that although patients with CHD have higher fasting and PP levels of triglycerides, RLP cholesterol, and RLP triglycerides than controls, the response (percent increase) to a fat-rich meal is comparable in both groups. Thus, a feeding challenge is not essential for assessment of these lipoproteins. Moreover, it is not necessary to obtain a fasting sample to assess direct LDL and HDL cholesterol.

Ascorbic acid supplementation does not lower plasma lipoprotein(a) concentrations

Elevated plasma concentrations of lipoprotein(a) (Lp[a]) are associated with premature coronary heart disease (CHD). Lp(a) is a lipoprotein particle consisting of low-density lipoprotein (LDL) with apolipoprotein (apo) (a) attached to the apo B-100 component of LDL. It has been hypothesized that ascorbic acid supplementation may reduce plasma levels of Lp(a). The purpose of this study was to determine whether ascorbic acid supplementation at a dose of 1 g/day would lower plasma concentrations of Lp(a) when studied in a randomized, placebo-controlled, blinded fashion. One hundred and one healthy men and women ranging in age from 20 to 69 years were studied for 8 months. Lp(a) values at baseline for the placebo group (n = 52) and the ascorbic acid supplemented group (n = 49) were 0.026 and 0.033 g/l, respectively. The 8-month concentrations were 0.027 g/l (placebo) and 0.038 g/l (supplemented group). None of these values were significantly different from each other. In addition, no difference in plasma Lp(a) concentration was seen between the placebo and supplemented groups when only subjects with an initial Lp(a) value of > or = 0.050 g/l were analyzed. Our data indicate that plasma Lp(a) concentrations are not significantly affected by ascorbic acid supplementation in healthy human subjects.

The effect of vitamin E, probucol, and lovastatin on oxidative status and aortic fatty lesions in hyperlipidemic-diabetic hamsters

Diabetes mellitus is associated with an increased risk of premature atherosclerosis, which may be due in part to an increased rate of low density lipoprotein (LDL) oxidation. Previous studies have shown that vitamin E, probucol, and lovastatin can reduce the oxidative susceptibility of LDL in normoglycemic animal models; however, few studies have investigated this in conjunction with aortic fatty streak lesion formation in diabetic hyperlipidemic models. Forty-eight Syrian hamsters were made diabetic by intraperitoneal injection of low dose streptozotocin. Diabetic animals (12 animals/groups) received a high saturated fat and cholesterol diet for 12.5 weeks. At 2.5 week of dietary treatments, the diet was supplemented with either: (1) 500 IU/day vitamin E (D+E); (2) 1% probucol w/w of the diet (D+P); (3) 25 mg/kg lovastatin (D+L); or (4) diabetic control (D). An age-matched group of hamsters (n=6) receiving the same diet but not made diabetic (ND) was used as control. At the end of the study, aortic arch foam cell-rich fatty streak lesion, plasma glucose, total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), non-HDL-C, triglycerides (TG), phospholipids, alpha-tocopherol, plasma lipid peroxide and the susceptibility of LDL to copper-catalyzed oxidation were determined. Diabetes increased plasma glucose, and when combined with an atherogenic diet resulted in a further increase of plasma lipids. Vitamin E, probucol, and lovastatin significantly reduced plasma TG in the diabetic hamsters fed the atherogenic diet. Vitamin E treatment increased TC, probucol reduced HDL-C without affecting TC; whereas lovastatin reduced TC and selectively decreased non-HDL-C, and significantly reduced fatty streak lesion formation in the aortic arch. While vitamin E and probucol were effective in reducing several indices of oxidative stress including plasma lipid peroxides, cholesterol oxidation products and in vitro LDL oxidation, they had no effect on fatty streak lesion formation. Our results indicate that the LDL in diabetic animals is more susceptible to oxidation than in non-diabetic hamsters and that not only vitamin E and probucol but also lovastatin provide antioxidant protection. It appears that in this combined model of diabetes and hypercholesterolemia, progression of fatty streak lesion formation is mainly associated with changes in TC and non-HDL-C as affected by lovastatin, and is less dependent on the extent of LDL oxidation, changes in plasma TG level and oxidative stress status.

Lipoprotein(a)-cholesterol and coronary heart disease in the Framingham Heart Study

BACKGROUND

Increased plasma lipoprotein(a) [Lp(a)] concentrations have been reported to be an independent risk factor for coronary heart disease (CHD) in some prospective studies, but not in others. These inconsistencies may relate to a lack of standardization and the failure of some immunoassays to measure all apolipoprotein(a) isoforms equally.

METHODS

We measured plasma Lp(a)-cholesterol [Lp(a)-C] in a Caucasian population of offspring and spouses of the Framingham Heart Study participants, using a lectin-based assay (LipoproTM). We compared the prevalence of increased Lp(a)-C to the presence of sinking pre-beta-lipoprotein (SPB). We also related Lp(a)-C concentrations to the prevalence of CHD risk in the entire population.

RESULTS

The mean (+/- SD) Lp(a)-C concentration in the Framingham population (n = 3121) was 0.186 +/- 0.160 mmol/L, with no significant gender or age differences. The mean Lp(a)-C concentrations in the absence or presence of SPB were 0.158 +/- 0. 132 mmol/L and 0.453 +/- 0.220 mmol/L, respectively (P <0.0001). The mean Lp(a)-C concentration in men with CHD (n = 156) was 0.241 +/- 0. 204 mmol/L, which was significantly (P <0.001) higher, by 34%, than in controls. The odds ratio for CHD risk in men with Lp(a)-C >/=0. 259 mmol/L (>/=10 mg/dL), after adjusting for age, HDL-cholesterol, LDL-cholesterol, smoking, diabetes, blood pressure, and body mass index, was 2.293 (confidence interval, 1.55-3.94; P <0.0005). Lp(a)-C values correlated highly with a Lp(a)-mass immunoassay [ApotekTM Lp(a); r = 0.832; P <0.0001; n = 1000].

CONCLUSIONS

An increased Lp(a)-C value >/=0.259 mmol/L (>/=10 mg/dL) is an independent CHD risk factor in men with a relative risk of more than 2, but was inconclusive in women. Lp(a)-C measurements offer an alternative to Lp(a)-mass immunoassays and can be performed on automated analyzers.

Lipoprotein(a), homocysteine, and remnantlike particles: emerging risk factors

Although lipoprotein(a) [Lp(a)] was first described more than 35 years ago, adequate prospective data have only recently supported Lp(a) as an independent risk factor for coronary heart disease (CHD). In vitro studies suggest that Lp(a) contributes to atherogenesis directly by cholesterol uptake and indirectly by the inhibition of fibrinolysis. In patients with CHD or a significant risk for CHD, Lp(a) should be measured and treated with either niacin or estrogen if the patient has Lp(a) cholesterol levels of more than 10 mg/dL or an Lp(a) mass of more than 30 mg/dL. In addition, homocysteine and remnantlike lipoprotein cholesterol are strongly supported by prospective or population-based prevalence data as independent risk factors for CHD. Homocysteine levels of more than 14 mumol/L should be treated with vitamin supplements of folate, B6, and B12. Remnantlike lipoprotein cholesterol is the product of a novel immunoassay that separates the partially hydrolyzed triglyceride-rich remnant particles. The association of these particles with CHD risk in women may explain the small independent CHD risk that triglycerides have in women in the Framingham Heart Study. A clear therapeutic intervention has not been documented but may include diet, fibric acid derivatives, or hydroxymethylglutamyl coenzyme A reductase inhibitors.

Elevated plasma lipoprotein(a) and coronary heart disease in men aged 55 years and younger. A prospective study

OBJECTIVE

To establish whether elevated lipoprotein(a) [Lp(a)], detected as a sinking pre-beta-lipoprotein band on electrophoresis of fresh plasma, is an independent risk factor for the development of premature coronary heart disease (CHD) in men.

DESIGN AND SETTING

Prospective study of the Framingham offspring cohort.

PARTICIPANTS

A total of 2191 men aged 20 to 54 years old who were free of cardiovascular disease when they were examined between 1971 and 1975.

MAIN OUTCOME MEASURES

Incident CHD (myocardial infarction, coronary insufficiency, angina pectoris, or sudden cardiac death) occurring by age 55 years.

RESULTS

After a median follow-up of 15.4 years, there were 129 CHD events. The relative risk (RR) estimates (with 95% confidence intervals [CIs]) for premature CHD derived from a proportional hazards model that included age, body mass index, and the dichotomized risk factor covariables elevated plasma Lp(a) level, total cholesterol level of 6.2 mmol/L (240 mg/dL) or more, high-density lipoprotein (HDL) level less than 0.9 mmol/L (35 mg/dL), smoking, glucose intolerance, and hypertension were as follows: elevated Lp(a) level, RR, 1.9 (95% CI, 1.2-2.9), prevalence, 11.3%; total cholesterol level of 6.2 mmol/L or more, RR, 1.8 (95% CI, 1.2-2.7), prevalence, 14.3%; HDL level of less than 0.9 mmol/L, RR, 1.8 (95% CI, 1.2-2.6), prevalence 19.2%; smoking, RR 3.6 (95% CI, 2.2-5.5), prevalence, 46.7%; glucose intolerance, RR, 2.7 (95% CI, 1.4-5.3), prevalence, 2.6%; hypertension, RR, 1.2 (95% CI, 0.8-1.8), prevalence, 26.3%.

CONCLUSIONS

Elevated plasma Lp(a) is an independent risk factor for the development of premature CHD in men, comparable in magnitude and prevalence (ie, attributable risk) to a total cholesterol level of 6.2 mmol/L (240 mg/dL) or more, or an HDL level less than 0.9 mmol/L (35 mg/dL).

Quantification of lipoprotein(a) in plasma by assaying cholesterol in lectin-bound plasma fraction

Lipoprotein(a) [Lp(a)] is a low-density lipoprotein (LDL)-like particle in which apolipoprotein(a) [apo(a)] is disulfide-linked to apolipoprotein B (apoB). High concentrations of Lp(a) in plasma are associated with an increased risk of coronary heart disease (CHD). Lp(a) has traditionally been measured by immunoassay and expressed as total mass of Lp(a). Measuring Lp(a) by its cholesterol content will provide a way to directly compare Lp(a) with other lipoproteins that are measured by cholesterol. We have developed an assay to quantify Lp(a) by its cholesterol content [Lp(a)-C], using lectin affinity to isolate Lp(a) from other lipoproteins, and then measuring the cholesterol within the isolated fraction. We compared the Lp(a)-C assay with an ELISA for Lp(a) mass in 47 plasma samples from normotriglyceridemic, fasting individuals with high Lp(a) contents (mean +/- SD, 446 +/- 350 mg/L). The mean Lp(a)-C concentration was 110 +/- 89 mg/L and correlated very highly with Lp(a) mass (r = 0.9975). Lp(a)-C measurement is an alternative method to screen for this CHD risk factor.

Quantification of lipoprotein(a) in plasma by assaying cholesterol in lectin-bound plasma fraction

Lipoprotein(a) [Lp(a)] is a low-density lipoprotein (LDL)-like particle in which apolipoprotein(a) [apo(a)] is disulfide-linked to apolipoprotein B (apoB). High concentrations of Lp(a) in plasma are associated with an increased risk of coronary heart disease (CHD). Lp(a) has traditionally been measured by immunoassay and expressed as total mass of Lp(a). Measuring Lp(a) by its cholesterol content will provide a way to directly compare Lp(a) with other lipoproteins that are measured by cholesterol. We have developed an assay to quantify Lp(a) by its cholesterol content [Lp(a)-C], using lectin affinity to isolate Lp(a) from other lipoproteins, and then measuring the cholesterol within the isolated fraction. We compared the Lp(a)-C assay with an ELISA for Lp(a) mass in 47 plasma samples from normotriglyceridemic, fasting individuals with high Lp(a) contents (mean +/- SD, 446 +/- 350 mg/L). The mean Lp(a)-C concentration was 110 +/- 89 mg/L and correlated very highly with Lp(a) mass (r = 0.9975). Lp(a)-C measurement is an alternative method to screen for this CHD risk factor.

Lipoprotein(a) and coronary heart disease

Elevated plasma or serum lipoprotein(a) (Lp(a)) levels have been associated with premature coronary heart disease (CHD). Lp(a) levels can be assessed quantitatively by electrophoresis and quantitatively by immunoassays determining either total Lp(a) mass, apo(a) mass on Lp(a) protein mass, or by precipitation methods followed by measurement of Lp(a) cholesterol. We prefer the latter method because it can be standardized. Electrophoretic methods can detect total Lp(a) values > or = 30 mg/dl. These values correspond to Lp(a) cholesterol values > or = 10 mg/dl. Such values are above the 75th percentile and represent high risk values for CHD. Values above the 90th percentile for middle aged men and women in Framingham (n = 2678) are > or = 38 mg/dl for total Lp(a). About 16% of patients with premature CHD (n = 321) have such values and have familial Lp(a) excess. Lp(a) is atherogenic because it can be deposited in the arterial wall, and it also can interfere with fibrinolysis. Multiple apo(a) isoforms have been found and are due to a variable number of kringle 4 like repeats. Lower molecular weight apo(a) isoforms forms are associated with elevated Lp(a) values and are more frequent in CHD kindreds. Both Lp(a) levels and apo(a) isoforms are highly heritable in this Caucasian population. Lp(a) values can be decreased with niacin, and such therapy should be strongly considered in CHD patients with elevated Lp(a) levels (> or = 30 mg/dl) since niacin treatment has been shown to decrease CHD morbidity and mortality in unselected CHD patients.

The linkage with apolipoprotein (a) in lipoprotein (a) modifies the immunochemical and functional properties of apolipoprotein B

Lipoprotein (a) [Lp(a)] was isolated from several donors and its apolipoprotein (a) [apo(a)] dissociated by a reductive treatment, generating the apo(a)-free form of Lp(a) [Lp(a--)] that contains apolipoprotein B (apo B) as its sole protein. Using anti-apo B monoclonal antibodies, the properties of apo B in Lp(a), Lp(a--), and autologous low-density lipoprotein (LDL) were compared. Marked differences in apo B immunoreactivity were found between these lipoproteins, due to the presence of apo(a) in Lp(a). Apo(a) enhanced the expression of two epitopes in the amino-terminal part of apo B while it diminished the immunoreactivity of three other epitopes in the LDL receptor binding domain. Accordingly, the binding of the lipoproteins to the LDL receptor was also decreased in the presence of apo(a). In a different experimental system, the incubation of antibodies that react with 27 distinct epitopes distributed along the whole length of apo B sequence with plastic-bound Lp(a) and Lp(a--) failed to reveal any epitope of apo B that is sterically hindered by the presence of apo(a). Our results demonstrate that the presence of apo(a) modified the organization and function of apo B in Lp(a) particles. The data presented indicate that most likely the modification is not due to a steric hindrance but that some more profound conformational changes are involved. We suggest that the formation of the disulfide bridge between apo B and apo(a) in Lp(a) alters the system of disulfide bonds present in apo B and thereby modifies apo B structure.

Isolation and partial characterization of apolipoprotein (a) from human lipoprotein (a)

A procedure was developed for the dissociation of apolipoprotein (a) (apo (a)) from pure human lipoprotein (a) (Lp(a)) prepared by density gradient ultracentrifugation and gel filtration. Lp(a) was ultracentrifuged through a layer of saline which was adjusted to a density of 1.182 g/mL and contained 30 mM dithiothreitol (50 mM) and phenylmethylsulfonyl fluoride (1.25 mM). Following centrifugation, the lipid and apolipoprotein B (apo B) were recovered as a lipoprotein (Lp(a) B) in the supernatant fraction, while the apo (a) was recovered as a lipid-poor protein pellet. An investigation of the supernatant lipoprotein by electron microscopy and compositional analysis revealed that it was similar in size and composition to low density lipoprotein (LDL) isolated from the same density range and contained apo B100 with an amino acid and carbohydrate composition which was similar to apo B from LDL. Estimates of the apparent molecular weight of the apo (a) varied amongst individuals but was always greater than apo B100 (congruent to 450,000). The amino acid composition of apo (a), which was very distinct from apo B, was characterized by a higher content of serine, threonine, proline, and tyrosine, but lower amounts of isoleucine, phenylalanine, and lysine when compared with apo B of Lp(a) or LDL. The apo (a) contained a much higher proportion of carbohydrate, in particular N-acetylgalactosamine, galactose, and N-acetylneuraminic acid (which were three- to six-fold higher) than the apo B of Lp(a). It is concluded that apo (a) is distinct from other apolipoproteins owing to its low avidity for lipid and the nature of the interaction with apo B. Lp(a) consists of an LDL-like particle with a carbohydrate-rich apo (a) attached to the surface of apo B.