Resistance to insulin-mediated glucose uptake has been implicated in the pathogenesis of Type II (non±insulin-dependent) diabetes mellitus, hypertension and coronary heart disease [1]. Insulin resistance is present in several non-European ethnic groups in which prevalence of' Type II diabetes is higher than in Europeans matched with them for weight, for instance in people of South Asian (Indian, Pakistani, Bangladeshi and Sri Lankan) descent [2]. Insulin resistance is strongly associated with obesity, especially central obesity, but the mechanism of this association is poorly understood. One possibility is that non-esterified fatty acids (NEFA) produced by lipolysis of triglyceride stores in muscle cells block glucose uptake either through substrate competition, as proposed over 30 years ago [3], or through direct inhibition of glucose transport [4].The relation of insulin sensitivity to intramyocellular lipid (IMCL) has been examined in muscle biopsy Diabetologia (1999) AbstractAims/hypothesis. To compare the relation between intramyocellular lipid content, central obesity and insulin sensitivity in Europeans and South Asians. Methods. Cross-sectional study of 40 South Asian and European non-diabetic men matched for age and body mass index. We measured intramyocellular lipid by proton magnetic resonance spectroscopy of soleus muscle, insulin sensitivity by the short insulin tolerance test, per cent body fat by dual-energy x-ray absorptiometry and visceral fat by single-slice computed tomography of the abdomen. Results. South Asians compared with Europeans had a higher mean per cent body fat (26.8 % vs 22.5 %, p = 0.05) and lower insulin sensitivity (mean ± SEM 2.4 ± 0.2 vs 3.4 %/min ± 0.3, p = 0.013). Mean ( ± SEM) intramyocellular lipid content was higher in South Asians than in Europeans (72.1 ± 7.5 vs 53.6 ± 4.9 mmol/kg dry weight, p = 0.046). In Europeans intramyocellular lipid was correlated with per cent body fat (r = 0.50, p = 0.028), waist:hip ratio (r = 0.74, p < 0.001), visceral fat (r = 0.62, p = 0.004) and insulin sensitivity (r = ±0.53, p = 0.016). In South Asians intramyocellular lipid was not significantly related to insulin sensitivity or obesity, and the strongest associations of insulin sensitivity were with fasting plasma triglyceride and waist:hip ratio. Conclusion/interpretation. The association of intramyocellular lipid with insulin sensitivity and obesity in Europeans is consistent with the hypothesis that muscle triglyceride mediates the effect of obesity on insulin sensitivity. The absence of a similar relation of insulin sensitivity to intramyocellular lipid in South Asians suggests that other mechanisms underlie the high insulin resistance observed in this group. [Diabetologia (1999) 42: 932±935]

There has been a vast increase in applications of magnetic resonance spectroscopy (MRS) in biomedical research during the last few years. This is not surprising since MRS provides both in vivo and in vitro a non-invasive tool for various biochemical and biomedical studies. There are also expectations that clinical MRS will have an important role as a diagnostic tool. An essential prerequisite for the future success of MRS for applicability in biomedical sciences will be accurate and biochemically relevant data analysis (at as high a level of automation as possible). This review briefly describes principles of the methodology available for advanced quantitative data analysis in the frequency domain. Various biomedical applications are discussed in order to illustrate the practical aspects of the analyses and to show the applicability and power of biochemical prior knowledge-based lineshape fitting analysis.

We used (1)H-magnetic resonance spectroscopy to noninvasively determine total creatine (TCr), choline-containing compounds (Cho), and intracellular (IT) and extracellular (between-muscle fibers) triglycerides (ET) in three human skeletal muscles. Subjects' (n = 15 men) TCr concentrations in soleus [Sol; 100.2 +/- 8.3 (SE) mmol/kg dry wt] were lower (P < 0.05) than those in gastrocnemius (Gast; 125.3 +/- 9.2 mmol/kg dry wt) and tibialis anterior (TA; 123. 7 +/- 8.8 mmol/kg dry wt). The Cho levels in Sol (35.8 +/- 3.6 mmol/kg dry wt) and Gast (28.5 +/- 3.5 mmol/kg dry wt) were higher (P < 0.001 and P < 0.01, respectively) compared with TA (13.6 +/- 2. 4 mmol/kg dry wt). The IT values were found to be 44.8 +/- 4.6 and 36.5 +/- 4.2 mmol/kg dry wt in Sol and Gast, respectively. The IT values of TA (24.5 +/- 4.5 mmol/kg dry wt) were lower than those of Sol (P < 0.01) and Gast (P < 0.05). There were no differences in ET [116.0 +/- 11.2 (Sol), 119.1 +/- 18.5 (Gast), and 91.4 +/- 19.2 mmol/kg dry wt (TA)]. It is proposed that the differences in metabolite levels may be due to the differences in fiber-type composition and deposition of metabolites due to the adaptation of different muscles during locomotion.

The main purpose of this study was to evaluate non‐invasively with magnetic resonance spectroscopy (1H‐MRS) changes in the concentrations of intracellular (IT) and extracellular (between muscle fibres) triglycerides (ET) in skeletal muscles of trained males (age range: 24–38 years) during two standard exercise protocols of alternating velocities. Protocol 1 consisted of locomotion in a shuttle manner between two lines 30 m apart at four different velocities (1, 2, 3 and 4 m s−1) which were alternated every minute in a standard routine for 90 min, whereas Protocol 2 included locomotion between two lines 20 m apart at only three velocities (2, 2.7 and 4 m s−1) until volitional exhaustion. The heart rate during both protocols fluctuated between 140 and 200 beats min−1. Using pre‐exercise muscle water to quantify individual total creatine (TCr) that was utilized as an internal standard and assuming that TCr does not change during exercise, subjects’ mean IT and ET concentrations in soleus (Sol) muscle before Protocol 1 (n= 8) were 45.8 ± 4.8 mmol (kg dry weight)−1 (mean ± s.e.m.) and 93.1 ± 14.1 mmol (kg dry weight)−1, respectively. After the exercise, the concentrations of IT and ET were not significantly different from the values at rest. Before Protocol 2 (n= 4), IT concentrations in Sol, gastrocnemius (Gast) and tibialis (Tib) muscles were 46.4 ± 13.6, 35.0 ± 12.1 and 23.1 ± 4.8 mmol (kg dry weight)−1, respectively, and were not affected by the exhaustive exercise. The ET concentrations in Sol, Gast and Tib were 136.4 ± 38.1, 175.3 ± 86.5 and 79.3 ± 20.0 mmol (kg dry weight)−1, respectively, and they did not change significantly after exhaustion. The study showed that levels of IT and ET were not affected by alternating intensity exercise to fatigue. This suggests that IT and ET in human Sol, Gast and Tib muscles do not contribute significantly to the energy turnover during this type of exercise. Energy for this type of muscle contraction may arise primarily from muscle phosphocreatine (PCr) and glycogen breakdown, circulating glucose and fatty acids from triglycerides other than those encountered within and between muscle cells.

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