MScanFit motor unit number estimation and muscle velocity recovery cycle recordings in diabetic polyneuropathy.

OBJECTIVE: Motor Unit Number Estimation (MUNE) methods may be valuable in tracking motor unit loss in diabetic polyneuropathy (DPN). Muscle Velocity Recovery Cycles (MVRCs) provide information about muscle membrane properties. This study aimed to examine the utility of the MScanFit MUNE in detecting motor unit loss and to test whether the MVRCs could improve understanding of DPN pathophysiology. METHODS: Seventy-nine type-2 diabetic patients were compared to 32 control subjects. All participants were examined with MScanFit MUNE and MVRCs in anterior tibial muscle. Lower limb nerve conduction studies (NCS) in peroneal, tibial and sural nerves were applied to diagnose large fiber neuropathy. RESULTS: NCS confirmed DPN for 47 patients (DPN + ), with 32 not showing DPN (DPN-). MScanFit showed significantly decreased MUNE values and increased motor unit sizes, when comparing DPN + patients with controls (MUNE = 71.3 ± 4.7 vs 122.7 ± 3.8), and also when comparing DPN- patients (MUNE = 103.2 ± 5.1) with controls. MVRCs did not differ between groups. CONCLUSIONS: MScanFit is more sensitive in showing motor unit loss than NCS in type-2 diabetic patients, whereas MVRCs do not provide additional information. SIGNIFICANCE: The MScanFit results suggest that motor changes are seen as early as sensory, and the role of axonal membrane properties in DPN pathophysiology should be revisited.

Diet, disease and pigment variation in humans.

There are several hypotheses which explain the de-pigmentation of humans. The most prominent environmental explanation is that reduced endogenous vitamin D production due to diminished radiation at higher latitudes had a deleterious impact on fitness. This drove de-pigmentation as an adaptive response. A model of natural selection explains the high correlations found between low vitamin D levels and ill health, as vitamin D's role in immune response has clear evolutionary implications. But recent genomic techniques have highlighted the likelihood that extreme de-pigmentation in Eurasia is a feature of the last 10,000years, not the Upper Pleistocene, when modern humans first settled northern Eurasia. Additionally the data imply two independent selection events in eastern and western Eurasia. Therefore new parameters must be added to the model of natural selection so as to explain the relatively recent and parallel adaptive responses. I propose a model of gene-culture co-evolution whereby the spread of agriculture both reduced dietary vitamin D sources and led to more powerful selection on immune response because of the rise of infectious diseases with greater population densities. This model explains the persistence of relatively dark-skinned peoples at relatively high latitudes and the existence of relatively light-skinned populations at low latitudes. It also reinforces the importance of vitamin D as a micronutrient because of the evidence of extremely powerful fitness implications in the recent human past of pigmentation.