Obesity and decreased vibration perception associated with premature cardiovascular mortality in a single center prospective study of people with diabetes

Background and aims

The aim of this prospective, single center study was to define factors associated with early cardiovascular mortality in diabetes.

Materials and methods

1345 patients under age 75 were included who were undergoing assessment of their diabetes between January 2008 and May 2010 as part of standard practice in a specialist clinic at a regional teaching hospital in Serbia. Peripheral artery disease (PAD) was assessed by audible Doppler waveform and ABPI with cut-offs >1.4 and <0.9. Peripheral neuropathy was assessed by vibration perception threshold (VPT, using a semi-quantitative tuning fork: abnormal if ≤5), ankle reflexes (AR) and sudomotor function of the foot. Diabetic retinopathy (DR) was assessed by fundoscopy. Evidence of vascular disease: thromboendarterectomy and/or cerebrovascular insult (TEA/CVI), myocardial infarction (MI), heart failure (HF), diabetic foot ulcer (DFU), minor amputations (sAMP) and major amputations (mAMP) was also collected. Outcome was determined in 2021 and baseline characteristics were compared between those who had and had not suffered cardiovascular death under age 75 years within 10 years of review in two casually selected cohorts.

Results

Those who died (n2=70) were more frequently male (60 vs. 45.3%, p=0.08), younger (66.4±7.4 vs. 79.9±3.4, p<0.000), had a shorter period of follow-up (3.6±2.3 vs. 11.2±1.7 years, p<0.000) when compared to those still alive (n1=75). Those who died were also significantly (p<0.01) more likely to have had TEA/CVI (34.3 vs. 10.7%), HF (21.4 vs. 1.3%), MI (44.3 vs. 20%), PAD (48.6 vs. 9.3%), DFU (25.7 vs. 9.3%), mAMP (17.1 vs. 1.3%) at baseline. There were no differences in proliferative DR (17.1 vs. 8%, p=0.10) and laser photocoagulation (25.7 vs. 13.3%, p=0.06) Following multivariable logistic regression analysis significant differences between groups remained for only creatinine (123±45 vs. 88.9±16.9 mmol/L, p<0.003) and VPT <5 (7.8 [95% CI: 3.7–16.4)], p=0.008), estimated maximum lifetime BMI (3.4 [95% CI: 1.7–6.8)], p<0.000), alcohol usage (4.7 [95% CI: 1.5–14.7)], p=0.005), smoking habit (2.2 [95% CI: 1.1–4.3)], p<0.03) and earlier age of diabetes onset (43.4±12.5 vs. 49.2±9.9, p=0.0029). When the 72 patients with impaired vibration sense were compared with 73 with VPT>6, there were significant differences in TEA/CVI (4.2 [95% CI: 1.6–10.9)], p=0.003), PAD (3.9 [95% CI: 1.8–8.8)], p<0.001) and estimated maximum lifetime BMI (9.4 [95% CI: 3.4–25.7), p<0.000). Finally, when those who had had a previous MI at baseline (n=46) were compared with those who hadn't (n=99), MI was associated with increased death rate (3.2 [95% CI: 1.5–6.6)], p=0.002), as was PAD (2.9 [(1.3–6.1)], p=0.007).

Conclusion

Decreased VPT, the presence of PAD on clinical testing and higher maximum estimated lifetime BMI are strongly associated with premature cardiovascular death. These measures may be independent markers of greater risk of reduced life expectancy.

Funding Acknowledgement

Type of funding sources: None.

Engineered domain-based assays to identify individual antibodies in oligoclonal combinations targeting the same protein

Quantitation of individual monoclonal antibodies (mAbs) within a combined antibody drug product is required for preclinical and clinical drug development. We have developed two antitoxins, XOMA 3B and XOMA 3E, each consisting of three mAbs that neutralize type B and type E botulinum neurotoxin (BoNT/B and BoNT/E) to treat serotype B and E botulism. To develop mAb-specific binding assays for each antitoxin, we mapped the epitopes of the six mAbs. Each mAb bound an epitope on either the BoNT light chain (LC) or translocation domain (H(N)). Epitope mapping data were used to design LC-H(N) domains with orthogonal mutations to make them specific for only one mAb in either XOMA 3B or XOMA 3E. Mutant LC-H(N) domains were cloned, expressed, and purified from Escherichia coli. Each mAb bound only to its specific domain with affinity comparable to the binding to holotoxin. Further engineering of domains allowed construction of enzyme-linked immunosorbent assays (ELISAs) that could characterize the integrity, binding affinity, and identity of each of the six mAbs in XOMA 3B and 3E without interference from the three BoNT/A mAbs in XOMA 3AB. Such antigen engineering is a general method allowing quantitation and characterization of individual mAbs in a mAb cocktail that bind the same protein.

Domain-based assays of individual antibody concentrations in an oligoclonal combination targeting a single protein

Quantitation of individual monoclonal antibodies (mAbs) within a combined antibody drug product is required for preclinical and clinical drug development, including pharmacokinetic (PK), toxicology, stability, and biochemical characterization studies of such drugs. We have developed an antitoxin, XOMA 3AB, consisting of three recombinant mAbs that potently neutralize the known subtypes of type A botulinum neurotoxin (BoNT/A). The three mAbs bind nonoverlapping BoNT/A epitopes with high affinity. XOMA 3AB is being developed as a treatment for botulism resulting from BoNT/A. To develop antibody-specific assays, we cloned, expressed, and purified BoNT/A domains from Escherichia coli. Each mAb bound only to its specific domain with affinity comparable to the binding to holotoxin. mAb-specific domains were used to develop an enzyme-linked immunosorbent assay (ELISA) for characterization of the integrity and binding activity of the three mAbs in the drug product. An electrochemiluminescence bridging assay that is robust to interference from components in serum was also developed, and we demonstrate that it can be used for PK assays. This type of antigen engineering to generate mAb-specific domains is a general method allowing quantitation and characterization of individual mAbs in a mAb cocktail that binds the same protein and is superior to anti-idiotype approaches.

Neutralizing human monoclonal antibodies binding multiple serotypes of botulinum neurotoxin

Botulism, a disease of humans characterized by prolonged paralysis, is caused by botulinum neurotoxins (BoNTs), the most poisonous substances known. There are seven serotypes of BoNT (A-G) which differ from each other by 34-64% at the amino acid level. Each serotype is uniquely recognized by polyclonal antibodies, which originally were used to classify serotypes. To determine if there existed monoclonal antibodies (mAbs) capable of binding two or more serotypes, we evaluated the ability of 35 yeast-displayed single-chain variable fragment antibodies generated from vaccinated humans or mice for their ability to bind multiple BoNT serotypes. Two such clonally related human mAbs (1B18 and 4E17) were identified that bound BoNT serotype A (BoNT/A) and B or BoNT/A, B, E and F, respectively, with high affinity. Using molecular evolution techniques, it proved possible to both increase affinity and maintain cross-serotype reactivity for the 4E17 mAb. Both 1B18 and 4E17 bound to a relatively conserved epitope at the tip of the BoNT translocation domain. Immunoglobulin G constructed from affinity matured variants of 1B18 and 4E17 were evaluated for their ability to neutralize BoNT/B and E, respectively, in vivo. Both antibodies potently neutralized BoNT in vivo demonstrating that this epitope is functionally important in the intoxication pathway. Such cross-serotype binding and neutralizing mAbs should simplify the development of antibody-based BoNT diagnostics and therapeutics.

Structure of a psoralen cross-linked DNA in solution by nuclear magnetic resonance

One- and two-dimensional nuclear magnetic resonance (NMR) methods were used to determine a three-dimensional model of an eight-base-pair DNA fragment (d-GGGTACCC) cross-linked with psoralen in solution. Two-dimensional nuclear Overhauser effect experiments were used to assign the spectrum and estimate distances for 171 proton pairs in the cross-linked DNA. The NMR-derived model shows a 53 degree bend into the major groove that occurs primarily at the site of drug addition and a 56 degree unwinding that spans the eight-base-pair duplex.