Association of Metformin With the Development of Age-Related Macular Degeneration

Importance

Age-related macular degeneration (AMD) is a leading cause of blindness with no treatment available for early stages. Retrospective studies have shown an association between metformin and reduced risk of AMD.

Objective

To investigate the association between metformin use and age-related macular degeneration (AMD).

Design, Setting, and Participants

The Diabetes Prevention Program Outcomes Study is a cross-sectional follow-up phase of a large multicenter randomized clinical trial, Diabetes Prevention Program (1996-2001), to investigate the association of treatment with metformin or an intensive lifestyle modification vs placebo with preventing the onset of type 2 diabetes in a population at high risk for developing diabetes. Participants with retinal imaging at a follow-up visit 16 years posttrial (2017-2019) were included. Analysis took place between October 2019 and May 2022.

Interventions

Participants were randomly distributed between 3 interventional arms: lifestyle, metformin, and placebo.

Main Outcomes and Measures

Prevalence of AMD in the treatment arms.

Results

Of 1592 participants, 514 (32.3%) were in the lifestyle arm, 549 (34.5%) were in the metformin arm, and 529 (33.2%) were in the placebo arm. All 3 arms were balanced for baseline characteristics including age (mean [SD] age at randomization, 49 [9] years), sex (1128 [71%] male), race and ethnicity (784 [49%] White), smoking habits, body mass index, and education level. AMD was identified in 479 participants (30.1%); 229 (14.4%) had early AMD, 218 (13.7%) had intermediate AMD, and 32 (2.0%) had advanced AMD. There was no significant difference in the presence of AMD between the 3 groups: 152 (29.6%) in the lifestyle arm, 165 (30.2%) in the metformin arm, and 162 (30.7%) in the placebo arm. There was also no difference in the distribution of early, intermediate, and advanced AMD between the intervention groups. Mean duration of metformin use was similar for those with and without AMD (mean [SD], 8.0 [9.3] vs 8.5 [9.3] years; P = .69). In the multivariate models, history of smoking was associated with increased risks of AMD (odds ratio, 1.30; 95% CI, 1.05-1.61; P = .02).

Conclusions and Relevance

These data suggest neither metformin nor lifestyle changes initiated for diabetes prevention were associated with the risk of any AMD, with similar results for AMD severity. Duration of metformin use was also not associated with AMD. This analysis does not address the association of metformin with incidence or progression of AMD.

Mechanical properties of a biodegradable bone regeneration scaffold

Poly (Propylene Fumarate) (PPF), a novel, bulk erosion, biodegradable polymer, has been shown to have osteoconductive effects in vivo when used as a bone regeneration scaffold (Peter, S. J., Suggs, L. J., Yaszemski, M. J., Engel, P. S., and Mikos, A. J., 1999, J. Biomater. Sci. Polym. Ed., 10, pp. 363-373). The material properties of the polymer allow it to be injected into irregularly shaped voids in vivo and provide mechanical stability as well as function as a bone regeneration scaffold. We fabricated a series of biomaterial composites, comprised of varying quantities of PPF, NaCl and beta-tricalcium phosphate (beta-TCP), into the shape of right circular cylinders and tested the mechanical properties in four-point bending and compression. The mean modulus of elasticity in compression (Ec) was 1204.2 MPa (SD 32.2) and the mean modulus of elasticity in bending (Eb) was 1274.7 MPa (SD 125.7). All of the moduli were on the order of magnitude of trabecular bone. Changing the level of NaCl from 20 to 40 percent, by mass, did not decrease Ec and Eb significantly, but did decrease bending and compressive strength significantly. Increasing the beta-TCP from 0.25 g/g PPF to 0.5 g/g PPF increased all of the measured mechanical properties of PPF/NVP composites. These results indicate that this biodegradable polymer composite is an attractive candidate for use as a replacement scaffold for trabecular bone.

Biological activity of rhBMP-2 released from PLGA microspheres

Human recombinant bone morphogenetic protein-2 (rhBMP-2) has been proven effective in stimulating the regeneration of bone in both skeletal and extraskeletal locations. Through encapsulation within, and release from, biodegradable poly(DL-lactic-co-glycolic acid) (PLGA) microspheres, a proven vehicle for sustained delivery of various proteins, the local concentrations of rhBMP-2 could be maintained at optimal levels to stimulate bone regeneration and remodeling at the site of healing in diverse clinical settings. Thus the purpose of this work was to investigate the encapsulation of rhBMP-2 in PLGA microspheres and its biologic activity upon release. Using in vitro tests in simulated body fluids, the effect of rhBMP-2 released from PLGA microspheres upon osteoblast cell cultures was found to be statistically similar to the effect produced by positive controls consisting of nonencapsulated aqueous rhBMP-2 in simulated body fluids. This clarifies an important step in skeletal tissue engineering strategies aimed at the use of encapsulated rhBMP-2 to stimulate bone regeneration and remodeling.

The Diet of Nestling Rainbow Bee-Eaters, Merops-Ornatus, on Rottnest Island, Western-Australia, and Observations on a Non-Destructive Method of Diet Analysis

The diet of nestling rainbow bee-eaters, Merops ornatus, was determined by analysis of droppings and regurgitated pellets collected at one site on Rottnest I., W.A. in the summer of 1982/83, and five sites in the summer of 1983/84. In total, 2187 insects from 10 families were identified. These comprised: Hymenoptera (95%), including Scoliidae (14%), Tiphiidae (38%), Sphecidae (l8.5%), Apoidea (1%), Formicoidea (7.5%) and undetermined Hymenoptera (16%); Coleoptera, Buprestidae (1.5%); Diptera, Muscidae (<1%); Hemiptera (3%); Odonata (<1%); and Orthoptera (<1%). The relative proportions of the different prey types varied significantly between sites and between different sampling times at the same site. There were also site-related differences in the mean length of nestling prey and at three sites nestlings were fed different sizes of prep during their development. Estimates of prey length based on wing remains were significantly smaller than those based on head remains at four of the six sites, and shapes of prey length distributions based on wings and heads were significantly different at all six sites.

Effects of caloric intake and dietary composition on the development of proteinuria, age-associated renal disease and longevity in the male rat

The development of age-associated proteinuria and renal disease was studied in groups of male Wistar rats fed 12.5, 25, 50 and 75 kcal of food/day, respectively, and in calorie-restricted (40 kcal/day) rats receiving diets rich in fat, protein or carbohydrate. Proteinuria developed faster, kidneys were larger and the incidence of glomerular lesions and proteinaceous casts was greater in rats eating high calorie diets of 50 kcal/day or more. High protein diets, even when calorie-restricted, increased protein excretion and the incidence of glomerular lesions. In old rats acute food restriction (25 kcal/day) decreased protein excretion by 40% in 1 week, with no further reduction in the 2 week. Life duration was greatest in rats fed 50 kcal/day.

Dietary, caging and temperature factors in the ageing of collagen fibres in rat tail tendon

The effect of dietary fat, carbohydrate and protein on tail tendon collagen ageing was studied in male Wistar rats. When rats were fed low-calorie diets there was no evidence that the content of carbohydrate, fat or protein affected the ageing of collagen. However, on high-calorie diets there was evidence that high-fat diets (21%) either saturated or unsaturated aged collagen fibres at a faster than low-fat diets (7%). Isolated housing of rats, which is necessary to control food intake, was found to slow the rate of collagen ageing. This effect was associated with reduced tail tendon temperatures.