Retinal function in relation to improved glycaemic control in type 1 diabetes.

AIMS/HYPOTHESIS: To study long-term changes in retinal function in response to sustained glycaemia reduction in participants with type 1 diabetes. METHODS: Prospective study using objective measures of retinal function in 17 participants with type 1 diabetes mellitus and minimal to moderate retinopathy who switched from conventional subcutaneous injection to continuous subcutaneous infusion of insulin (CSII). RESULTS: Glycated haemoglobin HbA(1c) gradually decreased from 9.1% at baseline before CSII to 7.4% after 1 year on CSII. Glycaemia was markedly reduced within 1 week after initiation of CSII and remained stable thereafter. Dark adaptation and retinal electroretinographic function at 1, 4 and 16 weeks after initiation of CSII were comparable with baseline values, whereas a significant improvement in rod photoreceptor dark adaptation and dark-adapted b-wave amplitudes were seen after 52 weeks (time to rod-cone break -25% [p < 0.0001], time to a standardised rod intercept -13% [p < 0.0001], dark-adapted rod b-wave full-field amplitude +15% [p = 0.0125], standard combined rod-cone b-wave amplitude +8% [p = 0.049]). No detectable change was observed in cone adaptation, electroretinographic cone function or retinopathy. CONCLUSIONS/INTERPRETATION: After initiation of CSII, the retinal visual pathway of the rods improved with a delay of more than 4 months, over a time scale comparable with the duration of the diabetic retinopathy early worsening response to sustained glycaemia reduction. This indicates that glycaemia has a long-term effect on the disposition of functional capacity in the retinal visual pathway of rod photoreceptors, the cells that appear to be driving the development of diabetic retinopathy.

Cumulative glycaemia as measured by lens fluorometry: association with retinopathy in type 2 diabetes.

AIMS/HYPOTHESIS: The aim of this study was to assess the association between lifelong cumulative glycaemia estimated by lens fluorometry and the presence of retinopathy in individuals with type 2 diabetes. METHODS: We carried out a cross-sectional population-based study of 970 participants aged between 30 and 60 years, of which 170 were diagnosed with diabetes on screening (WHO 1999 criteria) and 35 had known type 2 diabetes. Procedures included clinical and laboratory examinations, non-invasive assessment of the intrinsic fluorescence of the lens of the eye, and seven-field fundus photography. RESULTS: Retinopathy was found in 46 (22%) of 205 participants with type 2 diabetes. In a logistic regression analysis controlling for age, sex and diabetes status (screen-detected or known), a two-fold increase in lens fluorescence increased the odds for retinopathy by 3.46 (95% CI 1.25-9.55, p = 0.017). The association was marginally significant (OR 3.00 [95% CI 1.00-9.01], p = 0.050) when also adjusted for smoking, systolic blood pressure, body mass index and HbA(1c). CONCLUSIONS/INTERPRETATION: Diabetic retinopathy was related to cumulative lifelong glycaemia as estimated by lens fluorometry in participants with type 2 diabetes. This supports the hypothesis that retinopathy is a marker of lifelong elevated glycaemia as well as of the unknown, pre-diagnostic duration of type 2 diabetes. The powerful association between lens fluorescence and retinopathy underscores the importance of strict long-term glycaemic control in the prevention of retinopathy in people with diabetes.

Straight versus tortuous retinal arteries in relation to blood pressure and genetics.

BACKGROUND/AIMS: To assess the relative influence of genetic and environmental factors on retinal arterial tortuosity and the association between tortuosity and various health indices in healthy young to middle-aged persons. METHODS: This cross-sectional study included 57 monozygotic and 52 dizygotic same-sex healthy twin pairs, aged 20 to 46 years, who were characterised by determination of retinal vessel diameters, arterial blood pressure, blood glucose, body mass index, smoking habits and retinal arterial tortuosity, using a three-level grading scale (straight, wavy, tortuous). Heritability of retinal arterial tortuosity was estimated using structural equation modelling. RESULTS: Of 218 subjects, 79 (36.2%) had straight retinal arteries, 110 (50.5%) had wavy arteries, and 29 (13.3%) had tortuous arteries. Heritability of tortuosity was 82% (CI(95 )64, 92%), with unshared environmental factors accounting for the remaining 18% (CI(95 )8, 36%). Increasing values of mean arterial blood pressure and body mass index were both associated with decreasing levels of retinal arterial tortuosity. CONCLUSION: There was a large variation in tortuosity of retinal arteries in these healthy subjects and the predominant determinant was genetic influence, accounting for 82% of the observed variation in tortuosity.

Retinal vessel dilation following repletion of vitamin A deficiency.

We hypothesized that because depletion of vitamin A blocks the initiation of phototransduction, such inhibition of functional activation should lead to decrease retinal metabolism and perfusion. In a case study of a vitamin A-depleted patient, we found that retinal vessel diameters, a surrogate measure of retinal perfusion, increased in concert with the restitution of electroretinographic function following vitamin A supplementation. When normalized to conditions after treatment, the relative magnitude of study parameters at presentation were: scotopic electroretinography B-wave amplitude 1.2%, photopic electroretrinography B-wave amplitude 23%, retinal vein diameter 88%, retinal artery diameter 94%. These observations support that activation of the visual process results in increased retinal metabolism and perfusion.

[Body building aided by intramuscular injections of walnut oil]. / Bodybuilding ved hjaelp af intramuskulaer injektion af valnøddeolie.

This case report describes a 26-year-old body builder who had practiced several months of intramuscular self-injection of walnut oil. Apparently this is a normal procedure amongst body-builders. Our patient complained of swelling and tenderness overlying an injection site. Injections of oil may cause foreign body reactions, leading to tumours named according to the injected material; e.g. paraffinoma, oleoma. Systemic distribution has been reported to result in pulmonary complications.

Body core temperature during food restriction in rats.

Deep body temperature and locomotor activity of rats fed a reduced food amount (n = 9) and of starved rats (n = 9), were measured by implanted transmitters. Both groups were then refed ad libitum. The reduction in body temperature was significant for both groups, but larger in the starved rats than in the food restricted rats. There was a displacement of the circadian temperature rhythm in the starved rats. There were no significant differences in locomotor activity between groups until the start of refeeding. Rats fed reduced food amounts rapidly increased their activity, while the starved group retained a low activity for several days. Thermal conductance was reduced by 30% in both groups. This reduction in thermal conductance may explain how starving and semistarving rats are able to maintain core temperatures close to normal, even if resting metabolic rates are drastically reduced. The measured reduction in body core temperature signifies a change in the thermoregulatory 'set-point' during starvation.

Influences of time intervals between meals and total food intake on resting metabolic rate in rats.

Resting metabolic rate was measured in rats receiving single or double food portions every day or every other day, adding up to the same total food intakes. Starving rats were also measured. At two different total food intakes, there were no differences between the rats that were fed a meal every day and those fed a double meal every other day. Thus, the time interval between meals does not determine the extent of the metabolic depression. Also, the resting metabolic rates of rats fed various reduced food regimens are very similar to each other and to the resting metabolic rate of starved rats. The results of this study thus indicate that metabolic depression during starvation and severe caloric restriction in rats is an initially uniform response that modulates itself late in the starvation or restriction period in accordance with the total food intake.

Resting oxygen consumption in rats during food restriction, starvation and refeeding.

Oxygen consumption was measured in male rats during starvation and during different regimens of restricted feeding and refeeding after starvation. Changes in oxygen consumption and body mass were mostly parallel, but rats with a very reduced food intake displayed the same reduction in oxygen consumption as starved rats, despite the smaller reduction in body mass. Also, rats fed different amounts of food after starvation had different oxygen consumptions, but displayed the same changes in body mass. Two different refeeding regimens with restricted food amounts either induced a further depression of oxygen consumption (i.e. below starvation oxygen consumption), or a stabilizing of oxygen consumption on the level of starvation. The changes in oxygen consumption during restriction and feeding after starvation indicate that reductions in resting metabolic rate may not always be predicted from either body mass change or food intake.