Browsing by Author "Kohn, Tertius"

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    Open Access
    Inactivity and overfeeding related changes in skeletal muscle composition and metabolism in captive felids - are they at risk of developing metabolic syndrome?
    (2016) Feldmann, Daneil; Kohn, Tertius; Tordiffe, Adrian S W
    Obesity and physical inactivity are established key risk factors in the development of skeletal muscle insulin-resistance and type II diabetes in human and domestic animal populations. Wild animals are similarly exposed to these risk factors as a result of captivity. This study aimed at describing the skeletal muscle properties of captive lions (Panthera leo) who present with obesity and are physically inactive, with a group of free roaming wild lions. Skeletal muscle biopsies were collected from the Triceps brachii and analysed for fibre type composition, fibre size, and maximum oxidative (citrate synthase (CS), 3-hydroxyacyl CoA dehydrogenase (3HAD) and glycolytic (phosphofructokinase (PFK) and lactate dehydrogenase (LDH) enzyme capacities. The type IIA fibres were the predominant fibre type in both the wild (48%) and captive (44%) lions. No significant differences were evident in the overall fibre type composition between groups, although a trend towards less type I (28% vs 36%) and more type IIX (28% vs 16%) fibres in the captive group were observed. The captive lions displayed significantly larger cross-sectional areas (CSA) of the type I (5847μm² vs 3318 μm²) and IIA fibres (8344μm² vs 4360μm²) with no difference evident in the CSA of the IIX fibres. Relationships were observed between body mass and the CSAs of type I (r = 0.68, P = 0.0002) and IIA (r = 0.44; P = 0.03) fibres. Metabolically, the captive lions displayed higher flux through the glycolytic pathway as represented by their higher PFK activities (551 ± 287 vs. 338 ± 123 μmol/min/g protein, P < 0.05). In contrast, their CS activities (11 ± 3 vs. 14 ± 2 μmol/min/g protein) were lower than free roaming lions, suggesting lower oxidative capacity. No differences in LDH and 3HAD activities were observed between the two groups. Relationships were observed between 3HAD activity and MHC IIx fibre content (r = -0.43, P = 0.001), 3HAD activity and MHC I content (r = 0.55, P = 0.001). A positive correlation was observed between CS activity and MHC I content (r = 0.35, P = 0.009). In light of previous research, the data collected from this project follows that observed in exercise training models, where a sedentary lifestyle decreases oxidative capacity of muscle and increases type II fibre content. However, due to the low sample size in the free roaming wild lion group, interpretation of the data is difficult. Therefore, future research must strive to increase the sample number of the free roaming group.
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    Open Access
    Metabolic and lifestyle profiling of overweight female runners compared to lean counterparts: exploring the implications and causes of their elevated body weight
    (2016) Leith, David; Smith, James; Kohn, Tertius; Noakes, Tim
    There appears to be an emerging phenotype of recreational runners who are overweight despite being regularly active. This conflicts with the common perception that exercise protects against weight-gain, and it may be caused by underlying insulin-resistance. Alternatively, recent research has brought attention to metabolically healthy obese (MHO) individuals, who have increased adiposity but no commonly associated metabolic abnormalities, such as insulin-resistance, hypertension, dyslipidaemia and systemic inflammation. This study aimed to determine whether overweight (OW, BMI ≥ 25 kg.m⁻²) female runners were at risk of developing metabolic pathology and compare the findings to lean (LN, BMI < 23 kg.m⁻²) counterparts. A secondary aim was to explore potential inherent or lifestyle factors that may have predisposed or contributed to weight-gain in OW runners. METHODS. Twenty (10 OW, 10 LN) female recreational runners (years of running experience 7.1 ± 4.4 OW; 8.0 ± 3.7 LN) matched for mean age (38.7 ± 4.6 OW; 37.7 ± 4.3 LN), current mileage in km.week⁻¹ (42.0 ± 10.9 OW; 44.5 ± 12.1 LN) and running calibre expressed as energy expenditure (kcal.min⁻¹) in their most recent half-marathon (9.0 ± 1.1 OW; 9.2 ± 1.1 LN) were recruited for this study. Body fat percentage (BF%) was determined using DXA. Participants completed questionnaires about health history, lifestyle and eating habits and validated questionnaires concerning recent sleep and stress. Their diet was recorded using 3-day diet records and analysed using the South African Food Data System (Medical Research Council of South Africa). Habitual sleep and physical activity were quantified using 7-day actigraphy (Actiwatch 2) and accelerometry (Actigraph GTX3+) respectively. Blood pressure and resting metabolic rate were measured after an overnight fast. Blood samples were analysed for cardio-metabolic parameters and an Oral Glucose Tolerance Test was performed for insulin-sensitivity. RESULTS. OW exhibited a greater body weight (74.4 ± 6.4 kg OW; 59.4 ± 7.8 kg LN, p < 0.001) but similar fat-free-mass (49.4 ± 5.6 kg OW; 45.4 ± 5.9 kg LN) to the LN group. OW had a higher BF% (32.1 ± 3.9 OW; 21.8 ± 3.9 LN, p < 0.0001), and systolic (118 ± 10 mmHg OW; 107 ± 5 mmHg LN, p < 0.05), but not diastolic (72 ± 6 mmHg OW; 68 ± 4 mmHg LN) blood pressure. There was no difference between groups in serum uric acid, alanine aminotransferase, % HbA1c, total cholesterol, HDL-cholesterol, triglycerides or free-fatty-acids. OW had higher levels of C-reactive protein (1.30 ± 0.97 mg.L⁻¹ OW; 0.59 ± 0.35 mg.L⁻¹ LN, p < 0.05), total cholesterol / HDL-cholesterol (2.70 ± 0.40 OW; 2.30 ± 0.42 LN, p < 0.05) and LDL-cholesterol (2.99 ± 0.65 mM OW; 2.43 ± 0.72 mM LN, p < 0.05), but these were within normal ranges. IDL-cholesterol constituted a significantly greater proportion of total cholesterol in OW compared to LN, but HDL- and LDL- cholesterol sub-fraction distributions were similar. Indices of hepatic (HOMA-IR, 1.06 ± 0.51 OW; 0.86 ± 0.24 LN), and whole-body (Matsuda, 7.84 ± 2.46 OW; 9.16 ± 2.28 LN) insulin-sensitivity were variable and similar between groups. Total area-under-the-curve of the OGTT insulin response tended to be higher in OW (p = 0.08). Two OW runners had insulin-resistance (Matsuda < 5); but no participants had the metabolic syndrome. RMR (kcal.kg FFM⁻¹.day⁻¹) was lower in OW (29.5 ± 2.1 OW; 31.6 ± 2.3 LN, p < 0.05), but there were no significant differences in lifestyle factors (diet, physical activity, sleep and stress). Total energy intake in kcal.day⁻¹ (1928 ± 354 OW; 2166 ± 489 LN) and % macronutrient composition as Protein/Fat/Carbohydrate/Alcohol (20/44/33/3 OW; 16/43/36/5 LN) were both similar between groups. OW and LN also exhibited similar activity in steps.day⁻¹ (10 742 ± 3552 OW; 12 073 ± 3273 LN) and percentage accelerometer wear-time spent in Sedentary/Light/Moderate-Vigorous physical activity (75/14/11 OW; 72/15/13 LN). Both groups attained circa 7 hours.night⁻¹ of sleep, with good sleep onset latency (7.3 ± 5.8 minutes OW; 5.8 ± 3.5 minutes LN) and sleep efficiency (91.6 ± 4.4% OW; 90.7 ± 2.8% LN), and they reported reduced to average levels of recent stress. DISCUSSION. OW runners presented with greater mean adiposity than LN counterparts, but the two groups were not as distinct as anticipated. OW runners did present with greater metabolic risk according to some traditional risk factors, including inflammation, systolic blood pressure, LDL-C and total cholesterol. However, the first three were within normal ranges and the clinical relevance of the latter is questionable. It was, therefore, concluded that on average the OW group was not at metabolic risk. Only two OW runners and no LN runners were insulin-resistant according to indices derived from the OGTT. These findings may primarily reflect the insulin-sensitising effects of regular exercise and the consequent fitness of the OW runners. Appetite-dysregulation is speculated to have played an integral role in their prior weight-gain. We did not identify any lifestyle discrepancies that could have explained this weight-gain. The cross-sectional nature of this study made it difficult to assess past behaviour during weight-gain, and inter-individual variation was considerable. In combination with the small sample size, these factors limited the generalisability of the results. Future exploration of the 'overweight-runner' phenotype is warranted to clarify the mechanisms of weight-gain in habitual runners and consequent lifestyle changes that may promote meaningful weight-loss.
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    Open Access
    Metabolic changes to GLUT-4 levels in urban Chacma baboons on the Cape Peninsula: raiding their way to type 2 diabetes?
    (2013) Van Velden, Julia; Reed, Cecile C; Kohn, Tertius
    The Chacma baboons (Papio ursinus) of the Cape Peninsula are established raiders of human food, leading to widespread conflict between this intelligent, adaptable species and humans. The modern Western diet that these baboons have become exposed to has many deleterious effects on health, including obesity and type 2 diabetes. The aim of this study was to investigate whether this population of baboons have lowered GLUT-­‐4 transporter protein levels in comparison to wild-­‐feeding baboons, as an indication of insulin abnormalities. GLUT-­‐4 levels were analysed via Western Blot and DXA scanning was used to compare physical characteristics between these two groups. No significant difference in GLUT-­‐4 levels was found, however the two groups differed in three physical variables, with the semi-­‐provisioned Peninsula group having higher total weight (kg)(p<0,05), total body lean mass (kg) (p<0,01) and bone mineral content (kg)(p<0,001) than the wild-­‐feeding controls. These results indicate that male individuals from the Peninsula population are bigger but not fatter than wild-­‐feeding male baboons from the Eastern Cape population. Although it could not be determined whether human food is causing insulin abnormalities in the Cape Peninsula’s population of Chacma baboons, this study indicates that this is a promising area of research, likely to affect the management strategies used on this population.
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    Skeletal muscle composition in various breeds of domestic dogs: (A comparative study)
    (2019) van Boom, Kathryn; Kohn, Tertius; Schoeman, Johan
    The rising rate of insulin resistance and type 2 diabetes in humans over the past two decades have been linked to increasing rates of obesity, aging and urbanisation. A similar pattern is occurring in domestic animals, specifically cats and dogs. Skeletal muscle is a vital organ in the regulation of blood glucose. Its composition in terms of muscle fibre type, metabolism and contractility can differ substantially between species, but is poorly studied in the domestic dog, in particular the various breeds. It was hypothesised that insulin resistance and type 2 diabetes may be associated with muscle fibre type, in particular, muscle with a low type I fibre content being a predisposing factor. Therefore, the aims of this study were to investigate the skeletal muscle fibre composition and metabolic profile in the Triceps brachii (TB) and Vastus lateralis (VL) of 16 breeds of domestic dogs (Canis lupus familiaris). A secondary aim was to correlate the skeletal muscle composition with breeds reported as having a high incidence of diabetes. Skeletal muscle samples were collected post mortem from the TB and VL of 38 dogs from different breeds, age and sex, and analysed for fibre type composition, fibre size, oxidative and glycolytic metabolic capacity (citrate synthase (CS), 3-hydroxyacetyl co A dehydrogenase (3-HAD), creatine kinase (CK) and lactate dehydrogenase (LDH) enzyme activities). There was no significant difference between the TB and VL in any of the measurements. Type IIA was the predominant fibre type for both muscle groups (TB: 43%; VL: 44%) followed by type I (TB: 33%; VL: 38%) and type IIX (TB: 24%; VL: 18%). The cross sectional area (CSA) of the fibres were all smaller compared to humans and other wild animals. Surprisingly, there was no difference in the CSA between the fibres types and muscle groups: Type I: TB: 1740 µm2 ; VL: 1712 µm2 , Type IIA: TB: 1690 µm2 ; VL: 1720 µm2 , Type IIX TB: 1726 µm2 ; VL: 1791 µm2 ). Metabolically, the muscle of the dog displayed a high oxidative capacity with high activities (all activities in µmol/min/g protein) for CS (TB: 61; VL: 49) and 3-HAD (TB: 53; VL: 46). Lower CK (TB: 6115; VL: 6279) and higher LDH (TB: 1550; VL: 1478) activities than humans indicated a lower and higher flux through the high energy phosphate and glycolytic pathway, respectively. These results indicate that the dog has a predominance of type IIA fibres along with a higher oxidative capacity. There appears to be no pattern in fibre type profile that could be associated with a predisposition of a specific breed to insulin resistance and diabetes, although many of the breeds with a known risk did not form part of the study sample. This is the first study to characterise the skeletal muscle composition of a large population of dogs (16 breeds), but the association of breed to diabetes was not found. Future studies should include younger and more animals, as well as a diabetic population of dogs.