Jaipaul Singh

Selective activation of AMPK-PGC-1α or PKB-TSC2-mTOR signaling can explain specific adaptive responses to endurance or resistance training-like electrical muscle stimulation

Endurance training induces a partial fast‐to‐slow muscle phenotype transformation and mitochondrial biogenesis but no growth. In contrast, resistance training mainly stimulates muscle protein synthesis resulting in hypertrophy. The aim of this study was to identify signaling events that may mediate the specific adaptations to these types of exercise. Isolated rat muscles were electrically stimulated with either high frequency (HFS; 6×10 repetitions of 3 s‐bursts at 100 Hz to mimic resistance training) or low frequency (LFS; 3 h at 10 Hz to mimic endurance training). HFS significantly increased myofibrillar and sarcoplasmic protein synthesis 3 h after stimulation 5.3‐ and 2.7‐fold, respectively. LFS had no significant effect on protein synthesis 3 h after stimulation but increased UCP3 mRNA 11.7‐fold, whereas HFS had no significant effect on UCP3 mRNA. Only LFS increased AMPK phosphorylation significantly at Thr172 by ∼2‐fold and increased PGC‐1α protein to 1.3 times of control. LFS had no effect on PKB phosphorylation but reduced TSC2 phosphorylation at Thr1462 and deactivated translational regulators. In contrast, HFS acutely increased phosphorylation of PKB at Ser473 5.3‐fold and the phosphorylation of TSC2, mTOR, GSK‐3β at PKB‐sensitive sites. HFS also caused a prolonged activation of the translational regulators p70 S6k, 4E‐BP1, eIF‐2B, and eEF2. These data suggest that a specific signaling response to LFS is a specific activation of the AMPK‐PGC‐1α signaling pathway which may explain some endurance training adaptations. HFS selectively activates the PKB‐TSC2‐mTOR cascade causing a prolonged activation of translational regulators, which is consistent with increased protein synthesis and muscle growth. We term this behavior the “AMPK‐PKB switch.” We hypothesize that the AMPK‐PKB switch is a mechanism that partially mediates specific adaptations to endurance and resistance training, respectively.

Inflammatory Process in Type 2 Diabetes

Abstract:  Population‐based studies have shown strong relationship between inflammatory markers and metabolic disturbances, obesity, and atherosclerosis, whereas inflammation has been considered as a “common soil” between these clinical entities and type 2 diabetes (T2D). The accumulation of macrophages in adipose tissue (AT), the common origin of macrophages and adipocytes, the prevalent presence of peripheral mononuclear cells, and apoptotic β cells by themselves seem to be the sources of inflammation present in T2D, since they generate the mediators of the inflammatory processes, namely cytokines. The main cytokines involved in the pathogenesis of T2D are interleukin‐1β (IL‐1β), with an action similar to the one present in type 1 diabetes, tumor necrosis factor‐α (TNF‐α), and IL‐6, considered as the main regulators of inflammation, leptin, more recently introduced, and several others, such as monocyte chemoattractant protein‐1, resistin, adiponectin, with either deleterious or beneficial effects in diabetic pathogenesis. The characterization of these molecules targeted diabetes treatment beyond the classical interventions with lifestyle changes and pharmaceutical agents, and toward the determination of specific molecular pathways that lead to low grade chronic inflammatory state mainly due to an immune systems unbalance.

Effects of Momordica charantia fruit juice on islet morphology in the pancreas of the streptozotocin-diabetic rat.

An investigation was made of the effect of Momordica charantia fruit juice on the distribution and number of alpha, beta and delta cells in the pancreas of streptozotocin (STZ)-induced diabetic rats using immunohistochemical methods. The results indicated that there was a significant (Students t-test, P < 0.004) increase in the number of beta cells in M. charantia-treated animals when compared with untreated diabetics, however, their number was still significantly less than that obtained for normal rats. There was also a significant (P < 0.006) increase in the number of delta cells in STZ-diabetic rats compared to non-diabetic rats. This increase in the number of delta cells was not affected by M. charantia treatment. The number of alpha cells did not change significantly in M. charantia-treated rats when compared with untreated diabetic rats. Our results suggest that oral feeding of M. charantia fruit juice may have a role in the renewal of beta cells in STZ-diabetic rats or alternately may permit the recovery of partially destroyed beta cells.

Effects of diabetes mellitus on salivary secretion and its composition in the human

This study investigated the effects of diabetes mellitus (types I and II) on human salivary gland function compared to healthy age-matched controls. The results have shown that both type I and type II diabetic patients secrete significantly (p < 0.05) less resting and stimulated saliva compared to healthy age-matched controls (AMC). It was also found that the diabetic patients have an increased resting and stimulated salivary protein concentration compared to healthy participants. However, the secretory capacity (stimulated minus resting values) was markedly reduced compared to controls. The level of calcium (Ca2+) in the saliva of diabetic patients was significantly (p < 0.05) elevated compared to the AMC. In contrast, the levels of magnesium (Mg2+), zinc (Zn2+) and potassium (K+) in the saliva of diabetic patients were significantly (p < 0.05) reduced compared to the values obtained in AMC. These results indicate that diabetes mellitus can lead to marked dysfunction of the secretory capacity of the salivary glands. In these patients a modified fluid, organic and inorganic salivary secretion may be responsible for the increased susceptibility to oral infections and impaired wound healing described by others in the literature. (Mol Cell Biochem 261: 137–142, 2004)

On the selectivity and efficacy of defense peptides with respect to cancer cells

Here, we review potential determinants of the anticancer efficacy of innate immune peptides (ACPs) for cancer cells. These determinants include membrane‐based factors, such as receptors, phosphatidylserine, sialic acid residues, and sulfated glycans, and peptide‐based factors, such as residue composition, sequence length, net charge, hydrophobic arc size, hydrophobicity, and amphiphilicity. Each of these factors may contribute to the anticancer action of ACPs, but no single factor(s) makes an overriding contribution to their overall selectivity and toxicity. Differences between the anticancer actions of ACPs seem to relate to different levels of interplay between these peptide and membrane‐based factors.

Medicinal chemistry of the anti-diabetic effects of momordica charantia: active constituents and modes of actions.

Diabetes mellitus (DM) is one of the oldest known human disease currently affecting more than 200 million people worldwide. Diabetes mellitus is derived from two Greek words meaning siphon and sugar. In DM, patients have high blood level of glucose and this passes out with urine. This is because the endocrine pancreas does not produce either or not enough insulin or the insulin which is produced is not exerting its biochemical effect (or insulin resistance) effectively. Insulin is a major metabolic hormone which has numerous functions in the body and one main role is to stimulate glucose uptake into body’s cells where it is utilized to provide energy. The disease is classified into type 1 and type 2 DM. Type 1 DM develops when the insulin producing β cells have been destroyed and are unable to produce insulin. This is very common in children and is treated with insulin. Type 2 DM (T2DM) develops when the body is unable to produce an adequate amount of insulin or the insulin which is provided does not work efficiently. This is due to life style habits including unhealthy diet, obesity, lack of exercise and hereditary and environmental factors. Some symptoms of DM include excess urination, constant thirst, lethargy, weight loss, itching, decreased digestive enzyme secretion, slow wound healing and other related symptoms. If left untreated, DM can result in severe long-term complications such as kidney and heart failure, stroke, blindness, nerve damage, exocrine glands insufficiency and other forms of complications. T2DM can be treated and controlled by prescribed drugs, regular exercise, diet (including some plant-based food) and general change in life style habits. This review is concerned with the role of plant-based medicine to treat DM. One such plant is Momordica charantia which is grown in tropical countries worldwide and it has been used as a traditional herbal medicine for thousands of years although its origin in unknown. This review examines the medicinal chemistry and use(s) of M. charantia and its various extracts and compounds, their biochemical properties and how they act as anti-diabetic (hypoglycemic) drugs and the various mechanisms by which they exert their beneficial effects in controlling and treating DM.

Calcium–magnesium interactions in pancreatic acinar cells

Although the role of calcium (Ca2+)in the signal transduction and pathobiology of the exo¬crine pancreas is firmly established, the role of magne¬sium (Mg2+) remains unclear. We have characterized the intracellular distribution of Mg2+ in response to hormone stimulation in isolated mouse pancreatic acinar cells and studied the role of Mg2+ in modulating Ca2+ signaling using microspectrofluorometry and dig¬ital imaging of Ca2+‐orMg2+‐sensitive fluorescent dyes as well as Mg2+‐sensitive intracellular microelectrodes. Our results indicate that an increase in intracellular Mg2+ concentrations reduced the cholecystokinin (CCK) ‐induced Ca2+ oscillations by inhibiting the capacitive Ca2+ influx. An intracellular Ca2+ mobiliza¬tion, on the other hand, was paralleled by a decrease in [Mg2+]i, which was reversible upon hormone with¬drawal independent of the electrochemical gradients for Mg2+,Ca2+,Na+, and K+, and not caused by Mg2+ efflux from acinar cells. In an attempt to characterize possible Mg2+ stores that would explain the reversible, hormone‐induced intracellular Mg2+ movements, we ruled out mitochondria or ATP as potential Mg2+ buffers and found that the CCK‐induced [Mg2+]i de¬crease was initiated at the basolateral part of the acinar cells, where most of the endoplasmic reticulum (ER) is located, and progressed from there toward the apical pole of the acinar cells in an antiparallel fashion to Ca2+ waves. These experiments represent the first characterization of intracellular Mg2+ movements in the exocrine pancreas, provide evidence for possible Mg2+ stores in the ER, and indicate that the spatial and temporal distribution of intracellular Mg concentra¬tions profoundly affects acinar cell Ca2+ signaling.— Mooren, F. C., Turi, S., Günzel, D., Schlue, W.‐R., Domschke, W., Singh, J., Lerch, M. M. Calcium‐mag¬nesium interactions in pancreatic acinar cells. FASEB J. 15, 659‐672 (2001)

Momordica charantia fruit juice stimulates glucose and amino acid uptakes in L6 myotubes

The fruit of Momordica charantia (family: Cucurbitacea) is used widely as a hypoglycaemic agent to treat diabetes mellitus (DM). The mechanism of the hypoglycaemic action of M. charantia in vitro is not fully understood. This study investigated the effect of M. charantia juice on either 3H-2-deoxyglucose or N-methyl-amino-a-isobutyric acid (14C-Me-AIB) uptake in L6 rat muscle cells cultured to the myotube stage. The fresh juice was centrifuged at 5000 rpm and the supernatant lyophilised. L6 myotubes were incubated with either insulin (100 nM), different concentrations (1–10 μg ml−1) of the juice or its chloroform extract or wortmannin (100 nM) over a period of 1–6 h. The results were expressed as pmol min−1 (mg cell protein)−1, n= 6–8 for each value. Basal 3H-deoxyglucose and 14C-Me-AIB uptakes by L6 myotubes after 1 h of incubation were (means ± S.E.M.) 32.14 ± 1.34 and 13.48 ± 1.86 pmol min−1 (mg cell protein)−1, respectively. Incubation of L6 myotubes with 100 nM insulin for 1 h resulted in significant (ANOVA, p < 0.05) increases in 3H-deoxyglucose and 14C-Me-AIB uptakes. Typically, 3H-deoxyglucose and 14C-Me-AIB uptakes in the presence of insulin were 58.57 ± 4.49 and 29.52 ± 3.41 pmol min−1 (mg cell protein−1), respectively. Incubation of L6 myotubes with three different concentrations (1, 5 and 10 μg ml−1) of either the lyophilised juice or its chloroform extract resulted in time-dependent increases in 3H-deoxy-D-glucose and 14C-Me-AIB uptakes, with maximal uptakes occurring at a concentration of 5 μg ml−1. Incubation of either insulin or the juice in the presence of wortmannin (a phosphatidylinositol 3-kinase inhibitor) resulted in a marked inhibition of 3H-deoxyglucose by L6 myotubes compared to the uptake obtained with either insulin or the juice alone. The results indicate that M. charantia fruit juice acts like insulin to exert its hypoglycaemic effect and moreover, it can stimulate amino acid uptake into skeletal muscle cells just like insulin. (Mol Cell Biochem 261: 99–104, 2004)

Pathogenesis and pathophysiology of accelerated atherosclerosis in the diabetic heart

It has been established that atherosclerotic coronary artery disease is more frequent and more severe in diabetic compared to non-diabetic subjects, but the reason for the excess risk of developing coronary macroangiopathy in diabetes remains incompletely characterized. Various biochemical mechanisms speculated to being at the “heart” of diabetic cardiac and coronary macroangiopathy are reviewed in the present article. In doing so, this article presents evidence that the labyrinthine interactions of hyperglycemia, insulin resistance, and dyslipidemia in diabetes result in a pro-atherogenic phenotype. Furthermore, the diabetic milieu yields a complex (dys)metabolic environment characterized by chronic inflammation, procoagulability, impaired fibrinolysis, neovascularization abnormalities, and microvascular defects that cumulatively alter blood rheology, artery structure, and homeostasis of the endothelium. The contributory influences of these factors in the pathophysiology of coronary artery disease in diabetes are also discussed.

Innervation and mast cells of the rat exorbital lacrimal gland: the effects of age

The distribution of nerves and mast cells was studied in the lacrimal glands of 3-5-, 14- and 24-month-old rats, using light microscopic histochemical and immunohistochemical techniques. In 14-month and, to a greater extent, in 24-month-old rats there were signs of chronic inflammation and patchy destruction of acinar, ductal and vascular tissue. The glands of the three different age groups contained acetylcholinesterase (AChE), vasoactive intestinal polypeptide (VIP)-, neuropeptide Y (NPY)-, calcitonin gene-related peptide (CGRP)-, tyrosine hydroxylase-, substance P- and the phosphoprotein B-50-immunoreactive nerves. B-50-immunoreactive nerves were distributed around acini, blood vessels and ducts, in a similar manner to VIP and AChE. Substance P- and CGRP-immunoreactive nerves were sparsely distributed in interlobular connective tissue and around ducts and blood vessels. Tyrosine hydroxylase- and NPY-containing nerves were found around blood vessels. The 3-5- and 14-month-old rats had a similar pattern of innervation, however, by 24 months there was a reduction in the number and intensity of immunoreactive nerves. The loss of nerves was particularly associated with damage to the gland. Mast cells were also found in the lacrimal, mostly associated with neurovascular tissue. These could be histochemically labelled with alcian blue/safranin or toluidine blue and were immunohistochemically labelled with histamine and serotonin. Substance P-, CGRP-, VIP- and NPY-immunoreactive nerves were found apposed to mast cells. A large increase in mast cells was observed in 24-month compared to 3-5-month-old rats and these were found throughout the acinar tissue. These results show that a decrease in innervation and also chronic inflammation, with mast cell infiltration, occurs in aged rats. These findings may be contributing factors to reduced tear output in aging.